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Haryana State Board HBSE 8th Class Science Solutions Chapter 15 Some Natural Phenomena Textbook Exercise Questions and Answers.

Haryana Board 8th Class Science Solutions Chapter 15 Some Natural Phenomena

HBSE 8th Class Science Some Natural Phenomena Textbook Questions and Answers

Question 1.
Which of the following cannot be charged easily by friction?
(a) A plastic scale
(b) A copper rod
(c) An inflated balloon
(d) A woollen cloth.
Answer:
(b) A copper rod

Question 2.
When a glass rod is rubbed with a piece of silk cloth the rod
(a) and the cloth both acquire positive charge.
(b) becomes positively charged while the cloth has a negative charge.
(c) and the cloth both acquire negative charge.
(d) becomes negatively charged while the cloth has a positive charge.
Answer:
(b) becomes positively charged while the cloth has a negative charge.

Question 3.
Write T against true and F against false in the following statements:
(а) Like charges attract each other. (T/F)
(b) A charged glass rod attract a charged plastic straw. (T/F)
(c) Lightning conductor cannot protect a building from lightning. (T/F)
(d) Earthquakes can be predicted in advance. (T/F)
Answer:
(a) False
(b) True
(c) False
(d) False

Question 4.
Sometime, a crackling sound is heard while taking off sweater during winters. Explain.
Answer:
This occurs due to electric discharge between sweater and body. Some energy is always released with electric discharge, which in this case is released in form of a cracking sound.

Question 5.
Explain why a charged body loses its charge if we touch it with our hand.
Answer:
When we touch a charged body, it loses its charge, due to process of earthing. Our body is good conductor of electricity and transfers the charges to the earth.

Question 6.
Name the scale on which the destructive energy of an earthquake is measured. An earthquake measures 3 on this scale. Would it be recorded by a seismograph? Is it likely to cause much damage?
Answer:
Destructive energy of an earthquake is measured in Ricther Scale. Yes, it will be recorded in this scale. Earthquake with megnitude of 3 on Richter Scale is not much destructive.

Question 7.
Suggest three measures to protect ourselves from lightning.
Answer:
Three measure to stay protected from lightning are:

• Stay indore or under covered area.
• Don’t take bath during lightning.
• We should not use T.V. or phone during lighning.

Question 8.
Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon?
Answer:
A charged balloon is atracted by another charged balloon because both carry same charge like charge always repel each other. While the uncharged balloon is attracted by charged balloon due to unlike charged.

Question 9.
Describe with the help of a diagram an instrument which can be used to detect a charged body.
Answer:
An electroscope can be used to detect if a body is charged or not. When the metal strips repel each other proves that the body is charged as repulsion is the sure test to detect if a body carries charge or not.

Question 10.
List three states in India where earthquakes are more likely to strike.
Answer:
Kashmir, Punjab and Gujarat are more prone to earthquake.

Question 11.
Suppose you are outside your home and an earthquake strikes. What precaution would you take to protect yourself?
Answer:
We will take following precautions :

• We will try to move to an open space.
• If we are driving, we will slow down the vehicle and move slowly away from that area.
• We will not take shelter under trees or buildings.

Question 12.
The weather department has predicted that a thunderstorm is likely to occur on a certain day. Suppose you have to go out on that day. Would you carry an umbrella? Explain.
Answer:
No, we will not take an umbrella, as this will increase the risk of lighting because wide objects are more prone to lightning strike.

Extended Learning – Activities and Projects

Question 1.
Open a water tap. Adjust the flow so that it forms a thin stream. Charge a refill. Bring it near the water stream. Observe what happens. Write a short report on the activity.
Answer:
For self attempt.

Question 2.
Make your own charge detector. Take a paper strip roughly 10 cm x 3 cm. Give it a shape as shown in Fig. 15.15. Balance it On a needle. Bring a charged body near it. Observe what happens. Write a brief report, explaining its working.
Answer:
For self attempt.

Question 3.
This activity should be performed at night. Go to a room where there is a fluorescent tube light. Charge a balloon. Switch off the tube light so that the room is completely dark. Bring the charged balloon near the tubelight. You should see a faint glow. Move the balloon along the length of the tube and observe how glow changes.
Caution: Do not touch the metal parts of the tube or the wires connecting the tube with the mains.
Answer:
For self Attempt.

Question 4.
Find out if there is an organisation in your area which provides relief to those suffering from natural disaster. Enquire about the type of help they render to the victims of earthquakes. Prepare a brief report on the problems of the earthquake victims.
For more information on these topics, visit:
→ science.howstuffworks.com/lightning.htm
→ science.howstuffworks.com/ earthquake .htm
→ www enchantedlearning.com/subjects/ astronomy/planets/ earth/continents.shtml
Answer:
For self attempt.

HBSE 7th Class Science Some Natural Phenomena Important Questions and Answers

Very Short Answer Type Questions

Question 1.
Name any three natural phenomena.
Answer:
Earthquakes, cyclones, lightning.

Question 2.
According to ancient Greeks who invented thunderbolts?
Answer:
Goddess of Wisdom Minerva.

Question 3.
What are the sparks seen in sky during thunderstorms?
Answer:
Lightning.

Question 4.
Which resin did Greeks knew, produced sparks on rubbing continuously?
Answer:
Amber.

Question 5.
What happens when we rub a plastic scale with our hair?
Answer:
It gets charged.

Question 6.
What happens when charged plastic scale is brought close to bits of paper?
Answer:
Papers get attracted towared scale.

Question 7.
What happens when we rub an inflated balloon and let it free near a wall?
Answer:
Balloon gets attached to the wall.

Question 8.
How many types of charges are gained by rubbing objects?
Answer:
Two.

Question 9.
Name the charges bodies acquire on rubbing.
Answer:
Positive charge and negative charge.

Question 10.
What happens when similar charged bodies are brought close?
Answer:
They repel each other.

Question 11.
What happens when two different charged bodies are brought close?
Answer:
They attract each other.

Question 12.
What will happen when a charged glass rod is brought close to a charged straw?
Answer:
They will attract each other.

Question 13.
What will happen when a charged pen refil is brought close to a charged balloon?
Answer:
They attract each other.

Question 14.
Which charge is conventionally called a positive charge?
Answer:
Charge on a charged glass rod.

Question 15.
A charged glass rod attracts a charged straw. What is the charge on the charged straw?
Answer:
Negative charge.

Question 16.
What is the electric charge generated by rubbing called?
Answer:
Static electricity.

Question 17.
What is the static electricity?
Answer:
Charges which are produced by rubbing and are not movable are called static electricity.

Question 18.
How is electric charges different from static charges?
Answer:
Electric charges can flow but static charges cannot move.

Question 19.
What is used to transfer electrical charges from one body to another?
Answer:
Metallic conductors.

Question 20.
What is the transfer of charges from one body to earth is called?
Answer:
Earthing.

Question 21.
What provision is made in buildings to prevent electrocution?
Answer:
Earthing of wires is done.

Question 22.
How a huge energy is produced during thunderstorm?
Answer:
By repulsion of negative charges from clouds and positive charges from ground.

Question 23.
What is the process of meeting of negative charges from clouds with positive charges from ground to release huge energy called?
Answer:
Electric discharge.

Question 24.
Which place is safe during thunderstorms and lightning?
Answer:
Covered vehicles and buildings.

Question 25.
What should be considered as alert signs to get a safe place during thunderstroms?
Answer:
Hearing thunder without lightning.

Question 26.
Is sitting on a motor-cycle safe during lightning?
Answer:
No.

Question 27.
Where should one take shelter in open during lightning?
Answer:
Under small trees.

Question 28.
Is it safe to use wired phones during lightning?
Answer:
No.

Question 29.
Can a lightning victim electrocute another person?
Answer:
No.

Question 30.
What harms can lightning cause in a lightning victim?
Answer:
Loss of memory, loss of hearing or sight, broken bones etc.

Question 31.
What is the device used to save multistoryed buildings from lightning.
Answer:
Lightning rod.

Question 32.
Where is the lightning rod attached to protect the building from lightning?
Answer:
On the top of the building.

Question 33.
One end of the lightning rod is left loose in the air, where is the other end fixed or attached?
Answer:
Other end of the rod is attached to the ground.

Question 34.
Which fish can give electrical shock?
Answer:
Electrical eel.

Question 35.
What is the capacity of producing electric current in an electrical eel?
Answer:
650 volts.

Short Answer Type Questions

Question 1.
How can charging take place by rubbing?
Answer:
When a plastic comb is rubbed with hair it starts attracting small pieces of paper. Similarly, when two straws are rubbed with polythene and are brought close they repel each Other. Rubbing charges the comb and straws by loading charges on comb and straws, The polythene and hair against which straws and combs are charged also get charged.

Question 2.
How many types of charges do things acquire on rubbing?
Answer:
Charges acquired by objects are of two types named positive charge and negative charge. Charge acquired by a glass rubbed with silk is called positive charge and the charge acquired by the silk is called the negative charge.

Question 3.
How are negative and positive charges related to each other?
Answer:
Positive charges repel each other and negative charges repel each other. In other words similar charges repel each other. On the other hand negative charge is attracted by positive charges or in simple words opposite charges attract each other.

Question 4.
What is static electricity? How is it different from electric current?
Answer:
The electrical charges acquired by bodies on rubbing are called static electricity. These charges are called static because, they cannot move. This is the difference static electricity and electrical current has. Electrical current can move or flow but static electricity cannot move or flow.

Question 5.
What is electrical discharge?
Answer:
Transfer of charges from a body is called electrical discharge. If we touch a charged object, the charge gets transferred to the earth through our body. We say that the object is discharged. This is also called earthing. Electrical discharge can take place between any two conducting bodies.

Question 6.
How electrical discharge takes place in clouds?
Answer:
During thunderstorms the negative charges get accumulated near the clouds and positive charges accumulate near ground. When these negative and positive charges meet, electrical discharge takes place between clouds and grounds. It produces huge amount of energy which is released as lightning and thunder.

Question 7.
How do clouds get charged during thunderstorms?
Answer:
During thunderstorm there is a vigorous movement of air current in upward and downward direction i.e. in opposite direction. This is similar to rubbing of objects, this vigorous movements of water droplets in clouds cause charging of the clouds.

Question 8.
How does lightning strike during thunderstroms?
Answer:
During thunderstorms, the opposite charged clouds and ground come in contact and electrical discharged takes place between clouds and ground and huge energy is released as lightning. This is called lightning strike. Electrical discharge can take place between clouds and ground, clouds and human body, clouds and building etc.

Question 9.
How can we protect ourselves from lightning during thunderstorm when we are out of our home?
Answer:
Following precautions should be used when we are out during thunderstorm:

• We should not stay in open vehicles or places.
• Should not carry unbrella.
• Should not take shelter under tall trees or under poles etc.
• If shelter has to be taken, then it should be taken under smaller trees.

Question 10.
What precautions should we take to secure ourselves from lightning stroke during thunderstorm when we are in our homes?
Answer:
Following precautions should be taken while in house :

• We should not use wired phone.
• Electrical appliances should be plugged off.
• Should not bathe in running water.

Question 11.
Why is it advised to take shelter under smaller trees while in open during thunderstorms?
Answer:
During thunderstorms, we should take shelter under smaller trees because electrical discharge can easily take place with tall trees, so they are easy targets of lightning. While smaller trees are not in reach of lightning often.

Question 12.
How does a lightning rod protect a building from lightning?
Answer:
Lightning rods are installed on the top of the buildings. One end of the rod is left in open and the other one is connected to the earth.When lightning strikes the building, the charges are directly transferred to earth by the rod, this is called earthing. Earthing thus saves the buildings from lightning strike.

Question 13.
Why the Electric Eel is so called?
Answer:
Eel found in South America emits electric discharge from its body. It can produce electric current of 650 volts. It emits discharge to attack its enemies, to give shock to the prey. It can also give shock to human beings too. As these Eels produce electric discharge, they are called electric Eels.

Question 14.
What is an earthquake? How is it measured?
Answer:
Sudden trembling and shaking of the earth is called an earthquake. Due to sudden movements in the uppermost layer of the earth, the earth starts trembling, this movement of earth is called an earthquake. The magnitude of the earthquake is measured through an instrument called seismograph and it is measured on Richter scale.

Long Answer Type Questions

Question 1.
What is static electricity? How many kinds of charges are there?
Answer:
The electrical charge produced due to rubbing of objects is called static electricity. This charge cannot move as the electric current moves. These types of charges are produced only when objects are rubbed. When we rub an inflated balloon with our hair and let it loose, it attaches to wall. This proves that balloon has been charged. Similarly when a glass rod is rubbed with silk, it gets charged.

Charges are of two types : Negative charges and positive charges. Conventionally charge acquired by a glass rod is called positive charges and the charges acquired by the silk with which glass rod is rubbed aquires a negative charge. Similarly charged bodies repel each other and oppositely charged bodies attract each ether.

Question 2.
What is earthing? How is it useful?
Answer:
Transfer of charges to earth through conducting bodies is called earthing. In buildings wiring is done to do earthing when we touch the electric current, it enters the earth through our bodies. The bodies of the living beings including humans are good conductors of electricity. So, they easily acquire charges and transfer them to the earth, if they are in contact of the earth. This is called earthing.

Earthing is very useful as it protects us from electrocution. It prevents electric shocks as it transfers current to the earth. Earthing also saves building from lightning.

Question 3.
How does lightning take place during a thunderstorm?
Answer:
Lightning during thunderstorm takes place due to a phenomenon known as electric discharge. Electric discharge means interaction between oppositely charged objects. During thunderstorms vigorous upward and downward movement of air particles take place. This causes charging of water droplets accumulate in clouds and positive charge accumulates near ground. When these positive charges and negative charges meet a huge amount of energy is released in form of thunder and lightning. This whole process is called electrical discharge.

Question 4.
How can we save ourselves from lightning?
Or
What precautionary measures should be taken to save ourselves from lightning?
Answer:
Lightning gives a warning before appearing. Huge thunder without light is a warning. We should look for a safe place. No place in open is safe.

• One should rush to take shelter in building or house.
• One should not come out of the covered vehicle if on the road.
• One should not keep sitting on open vehicles like scooters, bikes etc.
• One should not take shelter under large and tall trees as they are easy target for electrical discharge.
• One should take shelter under smaller trees while in open as they are not easy target of lightning.
• If in open and no tree or shelter nearabout, one should sit with head folded under arms and embedded between the legs. One should not lie down in open.
• We should plug out all the electrical appliances during lightning.
• We should not use wired telephones during lightning, while mobiles and cordless phones are safe.
• One should not take ones bath during lightning.

Question 5.
What is a lightning rod? How is it used?
Answer:
Lightning rod is a device which is used to save tall buildings from lightning. Tall buildings are easy target to lightning as there can be easy electrical discharge with clouds. Lightning rod is a rod having three spikes on its top and a long earthing- wire to be attached to the earth. The end with spikes is left in open and other end is attached to earth. Lightning rod is fitted on the top of the buildings. During thunderstorm, when electrical discharge takes place between clouds and the building, the lightning rod acquires the charges and transfers them to the earth through its embedded end and saves the buildings from the strike of the lightning.

Question 6.
What is an earthquake? How does it occur?
Answer:
Sudden shaking and trembling of the earth is called earthquake. It occurs due to disturbance deep inside the upper layer of the earth. Earthquake is a natural phenomenon, which can be very devastating depending upon its intensity and magnitude.

The uppermost layer of the earth is not made up of a single flat surface. It is made up of different fragments, called seismic plates. These plates are joined with each other at different points. These plates are always in a continuous motion. Sometimes due to collision of these plates or upward or downward motion of these plates earth starts shaking. This is called an earthquake. The areas falling between these plates are the areas which are the most vulnerable areas for earthquakes. These are called fault zones or in simple language danger zones.

Question 7.
What is a seismograph? How does it work?
Answer:
Seismograph is an instrument which is used to record the intensity of the earthquake. Seismograph has a long rod suspended, with a pen attached to it. A paper is placed under the pen. When an earthquake strikes, the rod starts vibrating. The pen also starts vibrating and paper starts moving under the pen recording the movement of the pen. Scientists further study the seismic waves recorded by pen and make estimates about the intensity of the earthquake. This graph also gives the idea about the energy involved in the earthquake. This idea helps in determining the destructive power of the earthquake.

Some Natural Phenomena Class 8 HBSE Notes

• Natural phenomena like lightning, earthquakes etc. always made people fearful. People had many superstitions regarding these phenomena. They related these phenomenon to wrath and pleasures of Gods.
• Greeks knew that sparks like that of lightning also Occur when amber is rubbed with fur.
• Rubbing the objects with other objects can cause charging like rubbing a plastic scale with hair can charge the scale.
• Similar charged bodies repel each other while oppositely Charged bodies attract each other.
• Charges are of two types : negative and positive.
• Charges on a charged glass rod is said to be positive and other kind of charges are called negative charges.
• Opposite charges attract each other and similar charges repel each other.
• Charges which are generated due to rubbing are called static electricity. Static electricity means where charges do not move as in electric current.
• Charges can be transferred from one body to another. Charges can be transferred from a charged body to earth and this is called earthing.
• Lightning during rain is due to release of huge energy during electric discharge.
• Lightning can be dangerous, but we can secure ourselves by using precautions.
• Lightning rods can protect tall building from lightning as tall objects are easy target for lightning.
• Earthquake is another natural phenomena which can prove disastrous.
• Earthquakes take place due to disturbance in upper crusts of the earth.

Haryana State Board HBSE 8th Class Science Solutions Chapter 17 Stars and the Solar System Textbook Exercise Questions and Answers.

Haryana Board 8th Class Science Solutions Chapter 17 Stars and the Solar System

HBSE 8th Class Science Stars and the Solar System Textbook Questions and Answers

Question 1.
Which of the following is NOT a member of the solar system?
(a) An asteroid
(b) A satellite
(c) A constellation
(d) A comet
Answer:
(c) A constellation

Question 2.
Which of the following is NOT a planet of the sun?
(a) Sirius
(b) Mercury
(c) Saturn
(d) Earth
Answer:
(a) Sirius

Question 3.
Phases of the moon occur because:
(a) we can see only that part of the moon which reflects light towards us.
(b) our distance from the moon keeps changing.
(c) the shadow of the Earth covers only a part of the moon’s surface.
(d) the thickness of the moon’s atmosphere is not constant.
Answer:
(c) the shadow of the Earth covers only a part of the moon’s surface.

Question 4.
Fill in the blanks :
(a) The planet which is farthest from the Sun is __________.
(b) The planet which appears reddish in colour is __________.
(c) A group of stars that appear to form a pattern in the sky is known as a __________.
(d) A celestial body that revolves around a planet is known as __________.
(e) Shooting stars are actually not __________.
(f) Asteroids are found between the orbits of __________ and __________.
Answer:
(a) Neptune
(b) Mars
(c) constellation
(d) Satellite
(e) Meteors
(f) Mars and Jupiter.

Question 5.
Mark the following statements as true (T) or false (F) :
(а) Pole star is a member of the solar system. ( )
(b) Mercury is the smallest planet of the solar system ( )
(c) Uranus is the farthest planet in our solar system. ( )
(d) INSAT is an artificial satellite. ( )
(e) There are nine planets in our solar system. ( )
(f) Constellation Orion can be seen only with the telescope. ( )
Answer:
(a) False
(b) False
(c) False
(d) True
(c) False
(f) False

Question 6.
Match items in Column A with one or more items of Column B :

Answer:

Question 7.
In which part of the sky can you find Venus if it is visible as an evening star?
Answer:
In western sky.

Question 8.
Name the largest planet of the solar system.
Answer:
Jupiter.

Question 9.
What is a constellation? Name any two constellations.
Answer:
A group of stars in a recognizible shape is called a constillation. Orion and the Great Bear are constellations.

Question 10.
Draw sketches to show the relative positions of prominent stars in (i) Ursa Major and (ii) Orion.
Answer:

Question 11.
Name two objects other than planets which are members of the solar system.
Answer:
Meteors and Asteroids.

Question 12.
Explain how you can locate the Pole Star with the help of Ursa Major.
Answer:
Pole star is situated at the end of the Ursa Major. If a straight line starting from the last two stars is extended towards the north direction, it will lead to the Pole Star.

Question 13.
Do all the stars in the sky move? Explain.
Answer:
All the stars in the sky do not move, but they appear to move from east to west. This is actually due to rotation of earth on its axis. Earth moves from west to east. So it appears as the stars are rising from east and as the day dawns they sets in the west.

Question 14.
Why is the distance between stars expressed in light years? What do you understand by the statement that a star is eight light years away from the earth?
Answer:
Stars are away from the earth millions of kilometres away. It is not convenient to express such a large distance in the units of km. So the distance of stars from the earth is expressed in time taken by light to travel in one year. Eight light years mean time taken by light to travel in eight years.

Question 15.
Boojho made the following sketch (figure) of the solar system. Is the sketch correct? If not, correct it.
Answer:
No, the sketch is incorrect. The following sketch is correct.

Extended Learning – Activities and Projects

Question 1.
If possible, visit a planetarium. There are planetariums in many cities. In a planetarium you can see the motion of the stars, constellations and planets on a large dome.
Answer:
For self attempt.

Question 2.
On a moonless night observe the sky for a few hours. Look out for a meteor, which appears as a streak of light. September-November is a good time for observing meteors.
Answer:
For self attempt.

Question 3.
Learn to identify the planets visible to the naked eye and some prominent constellations such as Great Bear (Saptarshi) and Orion. Also try to locate the Pole Star and the star Sirius.
Answer:
For self attempt.

Question 4.
Select a convenient place on the roof of your house or in some playground from where you can watch sunrise clearly. Remember that you will have to do this activity for a few months. So, choose the place carefully. On a sheet of chart paper draw the outline of the eastern horizon indicating big trees, poles, etc. Mark the outline of the sheet so that you can place it in the same position every time. After every two weeks, note the position from where the Sun rises and mark this on your chart paper (Fig.). Also note the date of your observation. Repeat this for a few months. It is advisable that you start observations in the month of November or May.

Does the Sun always rise from the same direction? Discuss your observations with you teacher, parents and elderly people in your family or in the neighbourhood.
Answer:
For self attempt.

Question 5.
Form a group of studens. Prepare a model of the solar system showing the planets, and their relative sizes. For this take a large chart paper. Make spheres representing different planets according in their relative size (Use Table). You may use newspaper, clay or plasticine to make spheres. You can cover these spheres with paper of different colours. Exhibit your model in the class.

Answer:
For self attempt.

Question 6.
Try to make a scale model of the solar system showing distances of the planets from the Sun (Use Table 17.1). Did you face any difficulty? Explain it.
Answer:
For self attempt.

Question 7.
Solve the following riddle and try to make similar riddles yourself:
My first is in VAN but not in PAN
My second is in EARTH and also in HEAVEN
My third is in ONE and not in TWO
My fourth is in BUN and also in FUN
My last is in STAR but not in RADAR
I am a planet that moves round the Sun.
You can read more on the following websites:
→ http://www.nineplanets.org
→ http://www.kidsastronomy.com
→ http://www.solarsystem.nasa.gov/planets
→ http://aa.usno.navy.mil/fazz/does/moon- phases.html
Answer:
For self attempt.

HBSE 7th Class Science Stars and the Solar System Important Questions and Answers

Very Short Answer Type Questions

Question 1.
Name any three celestial bodies.
Answer:
Stars, Satellite, Planets.

Question 2.
Name the planets of solar system which cannot be seen by naked eye?
Answer:
Neptune and Pluto.

Question 3.
Name the force which makes planets move around the sun.
Answer:
Gravitational force.

Question 4.
Which has higher density : Earth or Sun?
Answer:
Earth.

Question 5.
Name the planet narest to earth.
Answer:
Mars is nearest to earth.

Question 6.
Write the names of any two constellation.
Answer:
Great Bear and Orion.

Question 7.
A group of stars visible in winter season look like a cluster of twinkling gems.
Answer:
Pleiades constellation.

Question 8.
In which season of the year are the constellations scorpio and orion visible in the Northern Hemisphere?
Answer:
Orion – Winters.
Scorpio – Summers.

Question 9.
Define star.
Answer:
Stars are the heavenly bodies that are extremely hot and have light of their own.

Question 10.
Name the star which is nearest to the earth.
Answer:
Alpha Centuari.

Question 11.
Write the names of two planets which are closer to the sun than the earth.
Answer:
Mercury and Venus.

Question 12.
Name the planet nearst to the sun.
Answer:
Mercury.

Question 13.
Name the planet farthest from the sun.
Answer:
Neptune.

Question 14.
Which planet of the solar system is the hotest?
Answer:
Mercury.

Question 15.
Name the planet of the solar system Which is nearer to the Sun and Venus.
Answer:
Mercury.

Question 16.
Which planet in the solar system is nearest to the earth?
Answer:
Venus.

Question 17.
Name the planet, where there is no carbon dioxide.
Answer:
Mercury.

Question 18.
Name the planets, which has no moon?
Answer:
Mercury and Venus.

Question 19.
Give any two applications of remote sensing.
Answer:
(i) Preparing waste land maps.
(ii) Survey for ground water and mineral resources.

Question 20.
A constellation having seven prominent stars, is visible during the winter. Name the constellation.
Answer:
Orion.

Question 21.
A belt of assorted debris, which failed to assemble into a planet, is located between the orbits of two planets in the solar system. Name these two planets.
Answer:
Mars and Jupiter.

Question 22.
Which planet has rings around it?
Answer:
Saturn.

Question 23.
Name largest asteroid.
Answer:
Ceres.

Question 24.
Why do meteors shine?
Answer:
On entering earth’s atmosphere, meteors become hot and bum due to friction of earths atmosphere and start to shine.

Question 25.
What are meteorites?
Answer:
Big pieces of rock material which do not bum completely in atmosphere of earth, fall on its surface. These are called meteorites.

Question 26.
How are comets formed?
Answer:
When the path of objects near the edge of solar system is disturbed to push them near to sun, comets are formed.

Question 27.
After how much time Halley’s comet is seen?
Answer:
After every 76 years.

Question 28.
Why does pole star appear to be stationary?
Answer:
Pole star lies on the axis of rotation of earth and appears stationary when viewed from any part of earth.

Question 29.
What does the colour of a star signify?
Answer:
Colour of a star signifies its temperature.

Question 30.
Define a satellite.
Answer:
A satellite is a solid heavenly small sized body revolving round a planet.

Short Answer Type Questions

Question 1.
Distinguish between stars and planets.
Answer:

Question 2.
Explain the importance of stars for the people in ancient times.
Answer:
In ancient times when there were no compass, night sky was very useful in finding the direction. As pole star remains fix in the sky in north, it indicated north direction. As the stars change their position with time, it has been possible to find the time with relative position of stars.

Question 3.
How is the pole star located in the sky? Why is it so special?
Answer:
The earth rotates on its axis from west to east, therefore, the stars appear to move in opposite direction, i.e. east to west. But pole star lies on the axis of rotation of earth which is fixed, Therefore, pole star also seems to be fixed in the sky. It is always in north direction and is very useful for finding direction.

Question 4.
Distinguish between star and shooting star.
Answer:

Question 5.
What is a meteor? Why does it last for a very short time?
Answer:
Meteors are the heavenly bodies made of rocky material which enter earth’s atmosphere. When they travel through air they become hot and burn because of friction. Due to this, these rocky pieces melt and vaporises very fast and do not last long.

Question 6.
Distinguish between natural and artificial satellites.
Answer:
Natural satellites are far away from planets. They are comparatively larger in size and are present naturally. Artificial satellites are sent from earth with specific requirements. Their distanc, size and mass are lesser than the natural satellite.

Question 7.
What is solar system? Name the planets situated between the sun and the earth?
Answer:
The solar system consists of the sun, eight planets; and their satellites and other heavenly bodies like meteors, comets and asteroids. The sun is the centre of the solar system and all the planets revolve around the sun in elliptical paths called orbits. The planets situated between the sun and the earth are Mercury and Venus.

Question 8.
What are the phases of the Moon?
Answer:
Moon has no light of its own. It reflects light of the Sun falling on it. On new moon day, moon is between the sun and the earth and no reflected light from it reaches the earth. We cannot see moon on that day. The visible moon increases every day till fifteenth day from the new moon day, the full phase of the moon is visible.

Positions of the Moon in its orbit and its corresponding phases
So, the waxing and waning of moon periodically as it revolves around the earth is called phases of moon.

Question 9.
Why moon cannot be used as a communication satellite?
Answer:
Moon is a natural satellite of the earth but it cannot be used as a communication satellite because :

• It is very far away from earth.
• Its time period 27.3 days is too large.
• It has neither equitorial orbit nor polar orbit which makes a satellite useful for different purposes.

Question 10.
What are constellations? Name some easily recognizible constellations in the sky.
Answer:
Group of stars forming a recognizible shape is called a constellation. These group of stars are identified in different shapes. Constellations do not change their shape. They also appear to move from east to west as other stars appear to. Some major constellations are Ursa Major, Ursa Minor, Orion, Cassiopeia etc. Some of them are visible during summers while some are visible during winters.

Question 11.
What are various types of motions associated with the planet earth?
Answer:
The earth has four types of motion. These are :

(i) The earth’s daily rotation on its axis.
(ii) The earth’s annual revolution around the sun.
(iii) The earth’s precession (conical motion of earth’s axis).
(iv) As a part of solar system, the earth’s motion in space along with the sun.

Question 12.
Explain the constellation Ursa Major.
Answer:
Ursa Major is one of the most famous constellation. We can see this constellation during summers. It is also called the Great Bear or the Saptarishi. There are seven prominently shining stars in this constellation which are arranged in shape of a question mark. At the tail of this constellation lies the Pole Star.

Question 13.
Describe the constellation also called the hunt.
Answer:
A well known constellation named Orion is also called the hunter. This constellation can be seen in the late evenings of winter. It has seven or eight brightly shining stars arranged in shape recognized with hunter. The brightest star in the sky Sirius is located at the extended line from the tail of this constellation.

Question 14.
What are asteroids?
Answer:
Asteroids are the small objects which revolve around the sun in a large gap between the orbits of Mars and Jupiter. These are quite large in their number and are considered as the part of our solar system. Each asteroid has its own orbit.

Question 15.
What are comets?
Answer:
Comets are the part of our solar system which revolve around the sun in highly elliptical orbits. It appears with a bright head and a long tail. The length of the tail grows in size as it approaches the sun. The tail is always directed away from sun.

Question 16.
What are various superstitions connected with appearance of comets?
Answer:
They are considered to be the messangers of destruction and disasters. They are supposed to bring wars,epidemics and flood with them. So, their appearance is considered as unauspicious.

Question 17.
List five uses of artificial satellites.
Answer:

• Weather forecasting.
• Radio and television transmission.
• Long distance communication.
• Locating mineral resources.
• Gathering information about our space.

Long Answer Type Questions

Question 1.
Explain celestial sphere.
Answer:
The large imaginary sphere on which all the heavenly bodies like stars, planets and satellites seems to lie is known as celestial sphere. Since we are on the earth, the earth appears stationary to us. When we look at the sky, the various objects in the sky like the stars and the moon appear to be moving round the earth. In other words, the celestial sphere appears to be moving from east to west round the earth. This apparent motion of the celestial sphere from east to west is actually due to the daily rotation of the earth from west to east. Since the earth rotates from west to east, the celestial sphere appears to rotate in the opposite direction, from east to west.

Question 2.
What are constellations? Explain. Name some prominent constellations with their Indian names.
Answer:
The groups of stars which seem to be arranged in the sky in beautiful patterns and recogniseable shapes are known as constellations. With each constellation, the ancient astronomers assigned the name of an object which it appears to resemble. There are 88 constellations into which the whole of the sky has been divided. In Indian astronomy, the constellations are known as Nakshatras.

Some prominent constellations with their Indian names are given below :
(i) Ursa Major or Saptarishi.
(ii) Ursa Minor or Laghu Saptarishi
(iii) Orion or Mriga or Vyadha
(iv) Tarus or Vrashba
(v) Scorpio or Vrishchika.

Question 3.
What is pole star? What is specific j about its position in the sky?
Answer:
There is only one star in the sky which appears stationary to an observer on earth. This star is named as pole star (Polaris) or Dhruvtara in India. This star appears stationary because, i it lies in the direction of the axis of the Earth about which the earth rotates. Any point on or j along the axis of a rotating body appears to be stationary. So, the pole star that lies along the direction of the axis of rotation of the earth, always sppears to be stationary.

Question 4.
What are artificial satellites? Explain their usage.
Answer:
Man made objects orbitting in outer space around the earth or any other planet are called artificial satellites of earth or that particular planet. The satellite like INSAT 3E or Kalpana Chawla I are examples of artificial satellites. Artificial satellites have many practical applications that effect our lives in many ways, i Long distance transmission of television programmes, communication through telephones and internet could be possible because of them. Artificial satellites are also used for research, defence and remote sensing. Remote sensing means collecting information from a distance. Information is collected regarding weather, agriculture, land and ocean features including movement of fish.

 Stars and the Solar System Class 8 HBSE Notes

• We can see many celestial bodies in a clear night sky.
• Stars are one of the celestial bodies which emit light of their own.
• Sun is also one of the stars which emits light and is a great source of heat. It is the closest star which is the centre of our solar system.
• Stars are many light years away from the earth and thus look very small from earth.
• Stars appear to travel from east to west.
• Pole star is the most shining star in the night sky. The pole star appears to.be stationary. It is situated near axis of rotation of earth and is thus helpful in finding direction.
• A group of stars, appearing in different shapes are called constellations. Their shapes resemble different objects and thus are named after the names of the objects.
• Other improtant parts of night sky are the planets. Planets are those celestial bodies, which revolve around sun.
• Our solar system consists of eight planets revolving around sun. It also consists of many other celestial bodies like asteroids, comets and meteors.
• Comets are the celestial bodies that revolve in highly elliptical orbits around sun.
• Bright streak of light in a night sky are commonly called shooting stars or meteors.
• A celestial body revolving around another celestial body is called a satellite.
• Artificially sent bodies in space, which revolve around earth or any other planet or a natural satellite is called an artificial satellite
• Jupiter is the largest planet while Venus is brightest planet in the night sky.
• Moon is the natural satellite of the earth. Moon appears in different phases. The phases of Moon occur because we can see only that part of the moon which reflects light towards us.

Haryana State Board HBSE 8th Class Science Solutions Chapter 11 Force and Pressure Textbook Exercise Questions and Answers.

Haryana Board 8th Class Science Solutions Chapter 11 Force and Pressure

HBSE 8th Class Science Force and Pressure Textbook Questions and Answers

Question 1.
Give two examples each of situations in which you push or pull to change the state of motion of objects.
Answer:
(i) We push the door to open it.
(ii) We pull the desk to change its position.

Question 2.
Give two examples of situations in which applied force causes a change in the shape of an object.
Answer:
When we apply force on clay with our fingers, its shape gets changed, when we press balloon with our hands, its shape get changed.

Question 3.
Fill in the blanks in the following statements :
(a) To draw water from a well we have to _________ at the rope.
(b) A charged body _________ an uncharged body towards it.
(c) To move a loaded trolley we have to _________ it.
(d) The north pole of a magnet _________ the north pole of another magnet.
Answer:
(a) pull
(b) attracts
(c) push it
(d) repels.

Question 4.
An archer stretches her bow while taking aim at the target. She then releases the arrow, which begins to move towards the target. Based on this information fill up the gaps in the following statements using the followiong terms:
muscular, contact, non-contact, gravity, friction, shape, attraction
(a) To stretch the bow, the archer applies a force that causes a change in its _________
(b) The force applied by the archer to stretch the bow is an example of _________ force.
(c) The type offeree responsible for a change in the state of motion of the arrow is an example of a _________ force.
(d) While the arrow moves towards its target, the forces acting on it are due to _________ and that due to _________ of air.
Answer:
(a) shape
(b) muscular
(c) contact
(d) gravity and friction.

Question 5.
In the following situations identify the agent exerting a force and the object on which it acts. State the effect of the force in each case.
(a) Squeezing a piece of lemon between the fingers to extract its juice.
(b) Taking out paste from a toothpaste tube.
(c) A load suspended from a spring while its other end is on a hook fixed to a wall.
(d) An athlete making a high jump to clear the bar at a certain height.
Answer:
(a) Agent are fingers, object is lemon, effect of force can be observable in form of lemon juice being expelled by squeezing.

(b) Agent is hand of the person squeezing the tube, object is toothpaste tube and effect of the force can be observed’ as the paste coming out of the tube.

(c) Agent is the load suspended, object is the spring and effect can be seen in the form of elongation of spring on suspension of load.

Question 6.
A blacksmith hammers a hot piece of iron while making a tool. How does the force due to hammering affect the piece of iron?
Answer:
The force due to hammering causes the change in the shape of the iron and iron can be moulded in the shape of the required tool.

Question 7.
An inflated balloon was pressed against a wall after it has been rubbed with a piece of synthetic cloth. It was found that the balloon sticks to the wall. What force might be responsible for, the attraction between the balloon and the wall?
Answer:
Electrostatic force.

Question 8.
Name the forces acting on a plastic bucket containing water held above ground level in your hand. Discuss why the forces acting on the bucket do not bring a change in its state of motion.
Answer:
Forces acting on the plastic bucket are the muscular force and gravitational force. The forces do not bring the change in its state of motion because they are acting in opposite direction with equal magnitude. The effect of the gravitational force will pull it down if the muscular force will grow weak. The body will feel the stretch of gravitational force and will have to bend” to cancel the magnitude of gravitational force.

Question 9.
A rocket has been fired upwards to launch a satellite in its orbit. Name the two forces acting on the rocket immediately after leaving the launching pad.
Answer:
Gravitational force and frictional force.

Question 10.
When we press the bulb of a dropper with its nozzle kept in water, air in the dropper is seen to escape in the form of bubbles. Once we release the pressure on the bulb, water gets filled in the dropper.
The rise of water in the dropper is due to
(a) pressure of water
(b) gravity of the earth
(c) shape of rubber bulb
(d) atmospheric pressure
Answer:
(d) atmospheric pressure.

Extended Learning – Activities and Projects

Question 1.
Make a 50 cm x 50 cm bed of dry sand about 10 cm in thickness. Make sure that its top surface is levelled. Take a wooden or a plastic stool. Cut two strips of graph paper each with a width of 1 cm. Paste them vertically on any leg of the stool-one at the bottom and the other from the top. Now gently put the stool on the sand bed with its legs resting on the and Increase the size of sand bed if required. Now put a load, say a school bag full of books, on the seat of the stool. Mark the level of sand on the graph strip. This would give you the depth, if any, to which the legs of stool sink in sand. Next, turn the stool upside down so that now it rests on its seat on the sand bed. Note the depth to which the stool sinks now. Next, put the same load on the stool and note the depth to which it sinks in the sand. Compare the pressure exerted by the stool in the two situations.
Answer:
For self attempt.

Question 2.
Take a tumbler and fill it with water. Cover the mouth of the tumbler with a thick card similar to that of a postcard Hold the tumbler with one hand while keeping the card pressed to its mouth with your other hand. Turn the tumbler upside down while keeping the card pressed to its mouth. Make sure that the tumbler is held vertical.

Gently remove the hand pressing the card. What do you observe? Does the card get detached allowing the water to spill? With a little practice you will find that the card continues to hold water in the tumbler even after it is not supported by your hand. Also try this activity by using a piece of cloth to hold the tumbler in an upside down position.
Answer:
For self attempt.

Question 3.
Take 4-5 plastic bottles of different shapes and sizes. Join them together with small pieces of glass or rubber tube as shown in Fig. Keep this arrangement on a level surface. Now pour water in any one of the bottles.

Note whether the bottle in which water is poured gets filled first or all the bottle in which water is poured gets filled first or all the bottles get filled up simultaneously. Note the level of water in all the bottles from time to time. Try to explain your observations.
For more information on force and pressure visit:
→ www.glenbrook.kl2 .il.us/gbssci/phys/class/ newtlauws/u212a,html
→ www.hatesville.kl2.in.us/physics/phyNet/ Mechanics/Newton2/Pressure .html
→ www.kids.earth.nasa.gov/archive/ air_pressure/
Answer:
For self attempt.

Activities

Activity No. 11.1

Activity No. 11.5
Studying the Effect of Force on Objects

Very Short Answer Type Questions

Question 1.
Define force.
Answer:
Any push or pull is called force.

Question 2.
When does a body move?
Answer:
A body moves when force is applied.

Question 3.
What is the first requirement to put force into play?
Answer:
Interaction between two objects.

Question 4.
Give any example of push.
Answer:
Pushing a table to wall.

Question 5.
Give an example of pull.
Answer:
Pulling the door to shut.

Question 6.
When force is applied on the object in the same direction of motion, what happens?
Answer:
The speed will increase.

Question 7.
What will happen when force is applied in the direction opposite to the movement of object?
Answer:
The speed will decrease.

Question 8.
How is the strength of a force expressed?
Answer:
In magnitude.

Question 9.
What effect does force put of state of motion?
Answer:
The speed of the object may change.

Question 10.
What is the state of motion of an object?
Answer:
The speed and direction of an object is called state of motion.

Question 11.
Does the force change the direction of the moving object?
Answer:
Yes.

Question 12.
Does the force change the shape of the object?
Answer:
Yes.

Question 13.
What is the contact force?
Answer:
Force which comes in action when objects are in contact.

Question 14.
What is the muscular force?
Answer:
Force resulting due to action of muscles.

Question 15.
Give examples of muscular force.
Answer:
Bending, moving, kicking etc.

Question 16.
What kind of force is the muscular force?
Answer:
Contact force.

Question 17.
What is friction?
Answer:
Force acting equal and opposite to the moving object is friction.

Question 18.
What kind oi force is the friction?
Answer:
Contact force.

Question 19.
Give example of friction force.
Answer:
Stopping of a rolling ball.

Question 20.
Which force stops the moving striker on a carrom board?
Answer:
Friction.

Question 21.
Why does the soal of our shoes get torn away by walking?
Answer:
Due to friction between soal and road.

Question 22.
What are non-contact forces?
Answer:
Forces acting jrom distance without forming contact.

Question 23.
What is magnetic force?
Answer:
Force exerted by a magnet is called magnetic force.

Question 24.
What happens when similar poles of magnets come in contact?
Answer:
They repel each other.

Question 25.
What happens when opposite poles of magnets come in contact?
Answer:
They attract each other.

Question 26.
What is the electrostatic force?
Answer:
Force exerted by the charged bodies is called electrostatic force.

Question 27.
When a comb rubbed against hair is brought near the small pieces of paper, the paper attaches to the comb which force has attracted papers?
Answer:
Electrostatic force.

Question 28.
What kind of forces are magnetic force and electrostatic force?
Answer:
Non-contact forces.

Short Answer Type Questions

Question 1.
How do we feel force in our daily life?
Answer:
Many big or small actions make us feel the force. We have to push or pull many objects daily. A moving ball stops on its own, the ball changes the direction of its motion, when hits with a bat. We churn curd to make lassi and many other actions.

Question 2.
What is force? Define with example.
Answer:
Force is the pull or push of the objects. Actions like pushing, pulling, bending, running, lifting etc. are the examples of force. Moving or stopping or changing shape and direction of motion of objects are the various actions showing force in play.

Question 3.
What happens when two people push an object from same direction?
Answer:
When two people push or pull something together in same direction, the force applied by them get added and the action becomes easy.

Question 4.
How can force change the state of motion?
Answer:
Force can change the state of motion by changing the direction of the motion and by changing the speed of the motion. Force in the direction of the motion increases the speed and force in opposite direction decreases the speed.

Question 5.
What is the state of motion?
Answer:
State of motion of an object is its speed and its direction. State erf zero motion means state of rest. An object can be in two positions one at rest or at motion. Any change in this position can be the change in the state of motion.

Question 6.
What is muscular force? Why is it a contact force?
Answer:
The force exerted by the action of the muscles is called muscular force. Muscular activities like running, bending, walking etc. produce muscular force. Muscular force is a contact force because it is applied only when it is in contact with an object.

Question 7.
What is force of Motion? How does it arise?
Answer:
Force of friction is force opposite and equal to the force of moving body. Force of friction arises when there is a contact between two surfaces and some movement takes place in them. Force of friction is a contact force as it only arises when two surfaces come in contact with each other.

Question 8.
Why does a moving ball gradually come to rest?
Answer:
A moving bail comes to rest on its own due to force of friction. When ball moves on the ground, their surfaces come in contact to each other. The ball and the ground exert equal and opposite force on each other, which gradually brings the moving ball to a stop.

Question 9.
What is electrostatic force? What kind of a force is it?
Answer:
Electrostatic force is exerted by a charged body on another charged or uncharged body. For this it is not necessary for the two bodies to be in contact with each other. This force is applicable from a distance so it is a non-contact force.

Question 10.
What is pressure? What is the relation of pressure with area on which it is applied?
Answer:
Force exerted on per unit area is called pressure. Pressure is related with area on which it is applied. When the area is increased the pressure exerted is less. But when the area on which pressure is exerted is decrease the pressure increases. So we conclude that pressure increases with decrease in area.

Long Answer Type Questions

Question 1.
How will you prove that pressure of liquids decrease with increase in height ^ of its column?
Answer:
For this to be proven take aplastic

container. Take a pin and make holes in the container in horizontal line from bottom to middle of the container. Now put water in the container and observe, you will see the water will come out with maximum pressure while the hole at the top will have the minimum pressure of water.

Question 2.
What changes are caused dud to application of farce on object?
Answer:
Force when applied on an object cause many changes on the object. Following changes occur due to application of force:
(i) Force change the state of motion : Force can change the state of motion of the object. It can increase or decrease the speed of the moving object. It can change the direction of the moving object.

(ii) Force can change the shape of the object: Force can change the shape of the object on which it is applied. When force is applied on some object, it always have some effect on the shape of the object. The change in the object is some time visible and some time, it is pot visible, but change in shape of the object is always accompanied by application of force.

Question 3.
What are the contact forces? Explain different forces which are contact forces.
Answer:
Contact forces are the forces which come in play when two objects come in contact with each other. Following forces are the contact forces :
(i) Muscular Force : The force which is exerted due to action of muscles is called muscular force. Actions like bending, running, moving etc. are examples of muscular forces. It is a contact force because it comes in play when it comes in contact of the object.

(ii) Friction: Equal and opposite force being exerted on an object when its surface comes in contact with other surface. It is also a contact force because it is exerted when two surfaces come in contact with each other Halting of a moving ball on its own is an example of force of friction.

Question 4.
What are the non-contact forces? Explain different non-contact forces.
Answer:
Non-contact forces are those forces, which can be exerted from a distance without establishing a contact. Following forces are the non-contact forces :
(i) Magnetic force : Force exerted by a magnet on another magnet or magnetic substance like iron is called magnetic force. Like poles of a magnet repel each other and opposite poles of a magnet attract each other.

(ii) Electrostatic Force: Force exerted by a charged body on other charged body or uncharged body is called electrostatic force. If we rub a comb with our hair and bring it near some small bits of paper, it will attract the bits of paper towards itself. This is electrostatic force which acts without making a direct contact with other charged or uncharged object.

(iii) Force of Gravity : Earth pulls every freely falling object towards its centre. This force exerted by earth is called force of gravity. This is also a non-contact force as it acts from a distance.

Force and Pressure Class 8 HBSE Notes

• Every push or pull is called force.
• Force comes into action when an object interacts with other object.
• Forces when implied in same direction add to each other, but when applied in opposite directions, they cancel each other. Equal forces applied in opposite direction results in net zero force.
• Force has magnitude and direction.
• Force can bring many changes in body on which it is applied.
• Force can change the speed of the moving body. Force in same direction of motion can increase the speed and in opposite direction can decrease the speed.
• Force can change the direction of the object in motion or at rest.
• Force can change theshapeof theobject. Force when applied on an object is always accompanied by change’in its shape.
• Two objects when come in contact with each other, they apply force on each other, this is called contact force. Muscular force, friction force etc. are examples of contact force.
• Force acting opposite to the direction of motion of a moving object is called force of friction.
• Force which acts from a distance is called a non-contact force.Magnetic force, electrostatic force and gravitational force are the examples of non-contact force.
• Force exerted per unit area is called pressure.
• Liquids and gases also exert pressure in all directions.
• Pressure exerted by air is called atmospheric pressure.

Haryana State Board HBSE 10th Class Social Science Solutions Geography Chapter 3 जल संसाधन Textbook Exercise Questions and Answers.

Haryana Board 10th Class Social Science Solutions Geography Chapter 3 जल संसाधन

HBSE 10th Class Geography जल संसाधन Textbook Questions and Answers

प्रश्न 1. बहुवैकल्पिक प्रश्न

(i) नीचे दी गई सूचना के आधार पर स्थितियों को “जल की कमी से प्रभावित’ या ‘जल की कमी से अप्रभावित’ में वर्गीकृत कीजिए।
(क) अधिक वार्षिक वर्षा वाले क्षेत्र
(ख) अधिक वर्षा और अधिक जनसंख्या वाले क्षेत्र
(ग) अधिक वर्षा वाले परंतु अत्यधिक प्रदूषित जल क्षेत्र
(घ)कम वर्षा और कम जनसंख्या वाले क्षेत्र
उत्तरः
(क) जल की कमी से प्रभावित
(ख) जल की कमी से प्रभावित
(ग) जल की कमी से प्रभावित
(घ) जल की कमी से प्रभावित

(ii) निम्नलिखित में से कौन-सा वक्तव्य बहुउद्देशीय नदी परियोजनाओं के पक्ष में दिया गया तर्क नहीं है?
(क)बहुउद्देशीय परियोजनाएँ उन क्षेत्रों में जल लाती है जहाँ जल की कमी होती है।
(ख) बहुउद्देशीय परियोजनाएँ जल बहाव की नियंत्रित करके बाढ़ पर काबू पाती है।
(ग) बहुउद्देशीय परियोजनाओं से बृहत् स्तर पर विस्थापन होता है और आजीविका खत्म होती है।
(घ)बहुउद्देशीय परियोजनाएँ हमारे उद्योग और घरों के लिए विद्युत पैदा करती हैं।
उत्तर-
(ग) बहुउद्देशीय परियोजनाओं से बृहत् स्तर पर विस्थापन होता है और आजीविका खत्म होती है। .

(iii) यहाँ कुछ गलत वक्तव्य दिए गए हैं। इसमें गलती पहचाने और दोबारा लिखें।
(क) शहरों की बढ़ती संख्या, उनकी विशालता और सघन जनसंख्या तथा शहरी जीवन शैली ने जल संसाधनों के सही उपयोग में मदद की है।
उत्तर-
शहरों की बढ़ती संख्या उनकी विशालता और सघन जनसंख्या तथा शहरी जीवन-शैली के कारण न केवल जल और ऊर्जा की आवश्यकता में बढ़ोत्तरी हुई है, अपितु इन से संबंधित समस्याएँ बढ़ी हैं।

(ख) नदियों पर बाँध बनाने और उनको नियंत्रित करने से उनका प्राकृतिक बहाव और तलछट बहाव प्रभावित नहीं होता।
उत्तर-
नदियों पर बाँध बनाने तथा उनको नियंत्रित करने से उनका प्राकृतिक बहाव अवरूद्ध होता है, जिसके कारण तलछट बहाव कमी आती है।

(ग) गुजरात में साबरमती बेसिन में सूखे के दौरान शहरी क्षेत्रों में अधिक जल आपूर्ति करने पर भी किसान नहीं भड़के।
उत्तर-
गुजरात में साबरमती बेसिन में सूखे के दौरान शहरी क्षेत्रों में अधिक जल आपूर्ति करने पर परेशान किसान उपद्रव करने को तैयार हो गए।

(घ)आज राजस्थान में इंदिरा गांधी नहर से उपलब्ध पेयजल के बावजूद छत वर्षा जल संग्रहण लोकप्रिय हो रहा है।
उत्तर-
आज पश्चिमी राजस्थान में छत वर्षाजल संग्रहण की रीति इंदिरा गाँधी नहर से उपलब्ध बारहमासी पेयजल के कारण कम होती जा रही है।

प्रश्न 2. निम्नलिखित प्रश्नों के उत्तर लगभग 30 शब्दों में दीजिए।

(i) व्याख्या करें कि जल किस प्रकार नवीकरण योग्य संसाधन है?
उत्तर-
पृथ्वी का तीन-चौथाई भाग जल से आच्छादित है। परन्तु इसमें प्रयोग लाने योग्य अलवणीय जल का अनुपात बहुत कम है जिसका निरन्तर नवीकरण और पुनर्भरण जलीय चक्र द्वारा होता रहता है। सम्पूर्ण जल जलीय चक्रय में गतिशील रहता है जिससे जल नवीकरण सुनिश्चित होता है।

(ii) जल दुर्लभता क्या है और इसके मुख्य कारण क्या हैं?
उत्तर-
जल दुर्भलता से तात्पर्य, मनुष्य द्वारा प्रयोग करने के लिये जल की कमी का होना है। . अधिकतर जल की कमी इसके अतिशोषण, अत्यधिक प्रयोग और समाज के विभिन्न वर्गों में जल के असमान वितरण के कारण होती है।

(iii) बहुउद्देशीय परियोजनाओं से होने वाले लाभ और हानियों की तुलना करें।
उत्तर-
बहुउद्देशीय परियोजनाओं के लाभ
(अ)जल विद्युत उत्पादन
(ब) सिचाईं
(स) बाढ़ नियन्त्रण
(द) मत्स्य पालन
(क) गृह एवं औद्योगिक उपयोग
(ख) आंतरिक नौका चालना

बहुउद्देशीय परियोजनाओं की हानियां :

(अ) नदियों का प्राकृतिक बहाव अरूद्ध होना
(ब) नदियों के तलछट में पानी का कम बहाव
(स) बाढ़ के मैदानों में बने जलाशयों के कारण उस क्षेत्र की वनस्पति एवं अपघटन।

3. निम्नलिखित प्रश्नों के उत्तर लगभग 120 शब्दों में दीजिए।

(i) राजस्थान के अर्ध-शुष्क क्षेत्रों में वर्षा जल संग्रहण किस प्रकार किया जाता है? व्याख्या कीजिए।
उत्तर-
राजस्थान के अर्ध-शुष्क और शुष्क क्षेत्र में लगभग प्रत्येक घर में पीने का पानी संग्रहित करने हेतु भूमिगत टैंक या ‘टाँका’ हुआ करते थे। इसका आकार एक बड़े कक्ष जितना हो सकता है। टाँका यहाँ सुविकसित छत वर्षाजल संग्रहण तन्त्र का अभिन्न अंग है जिसे मुख्य घर या आँगन में बनाया जाता था। वे घरों की ढलवाँ छतों से पाइप द्वारा जुड़े हुए थे। छत से वर्षा का पानी इन नलों द्वारा भूमिगत टाँका तक पहुँचता था। वर्षा का प्रथम तल छत और नलो की सफाई हेतु प्रयुक्त किया जाता है। इसके बाद होने वाली वर्षा जल संग्रहणीय होता टाँका में वर्षाजल अगली वर्षा ऋतु तक संग्रहित किया जा सकता है। यह इसे जल की कमी वाली ग्रीष्म ऋतु तक पीने का जल उपलब्ध करवाने वाला जल स्रोत बनाता है। वर्षा जल को प्राकृतिक जल का शुद्धतम रूप समझा जाता है।

(ii) परंपरागत वर्षा जल संग्रहण की पद्धतियों को आधुनिक काल में अपना कर जल संरक्षण एवं भंडारण किस प्रकार किया जा रहा है।
उत्तर-
प्राचीन भारत में उत्कृष्ट जलीय निर्माणों के साथ-साथ जल संग्रहण ढाँचे भी पाए जाते थे। लोगों ने स्थानीय पारिस्थितिकीय परिस्थितियों और उनकी जल आवश्यकतानुसार वर्षाजल, भौमजल, नदी जल, तथा बाढ़ जल संग्रहण के अनेक उपाय विकसित कर लिए थे। इन्हीं परंपरागत वर्षा जल संग्रहण के तरीकों को आधुनिककाल में अपना कर संरक्षण निम्नलिखित प्रकार से किया जा रहा है-

• पी.वी.सी. पाइप का उपयोग करके छत का वर्षा जल संग्रहित किया जाता है।
• रेत और ईंट प्रयोग करके जल का छनन किया जाता
• भूमिगत पाइप द्वारा जल हौज तक ले जाता है जहाँ से इसे तुरन्त प्रयोग किया जा सकता है।
• हौज से अतिरिक्त जल कुएँ तक ले जाया जाता है। (v) कुएँ का जल भूमिगत जल का पुनर्भरण करता है। (vi) बाद में इस जल का उपयोग किया जा सकता है।

Haryana Board HBSE 8th Class English Solutions Honeydew & It So Happened

HBSE 8th Class English Solutions Honeydew

HBSE Haryana Board 8th Class English Honeydew Prose

• Chapter 1 The Best Christmas Present in the World
• Chapter 2 The Tsunami
• Chapter 3 Glimpses of the Past
• Chapter 4 Bepin Choudhury’s Lapse of Memory
• Chapter 5 The Summit Within
• Chapter 6 This is Jody’s Fawn
• Chapter 7 A Visit to Cambridge
• Chapter 8 A Short Monsoon Diary
• Chapter 9 The Great Stone Face 1
• Chapter 10 The Great Stone Face 2

HBSE Haryana Board 8th Class English Honeydew Poem

• Poem 1 The Ant and the Cricket
• Poem 2 Geography Lesson
• Poem 3 Macavity: The Mystery Cat
• Poem 4 The Last Bargain
• Poem 5 The School Boy
• Poem 6 The Duck and the Kangaroo
• Poem 7 When I Set Out for Lyonnesse
• Poem 8 On the Grasshopper and Cricket

HBSE 8th Class English Solutions It So Happened

HBSE Haryana Board 8th Class English Supplementary Reader It So Happened

• Chapter 1 How the Camel Got His Hump
• Chapter 2 Children at Work
• Chapter 3 The Selfish Giant
• Chapter 4 The Treasure Within
• Chapter 5 Princess September
• Chapter 6 The Fight
• Chapter 7 The Open Window
• Chapter 8 Jalebis
• Chapter 9 The Comet 1
• Chapter 10 The Comet 2

Haryana Board HBSE 7th Class English Solutions Honeycomb & An Alien Hand

HBSE 7th Class English Solutions Honeycomb

HBSE Haryana Board 7th Class English Honeycomb Prose

• Chapter 1 Three Questions
• Chapter 2 A Gift of Chappals
• Chapter 3 Gopal and the Hilsa-Fish
• Chapter 4 The Ashes that Made Trees Bloom
• Chapter 5 Quality
• Chapter 6 Expert Detectives
• Chapter 7 The Invention of Vita Wonk
• Chapter 8 Fire: Friend and Foe
• Chapter 9 A Bicycle in Good Repair
• Chapter 10 The Story of Cricket

HBSE Haryana Board 7th Class English Honeycomb Poem

• Poem 1 The Squirrel
• Poem 2 The Rebel
• Poem 3 The Shed
• Poem 4 Chivvy
• Poem 5 Trees
• Poem 6 Mystery of the Talking Fan
• Poem 7 Dad and the Cat and the Tree
• Poem 8 Meadow Surprises
• Poem 9 Garden Snake

HBSE 7th Class English Solutions An Alien Hand

HBSE Haryana Board 7th Class English Supplementary Reader An Alien Hand

• Chapter 1 The Tiny Teacher
• Chapter 2 Bringing Up Kari
• Chapter 3 The Desert
• Chapter 4 The Cop and the Anthem
• Chapter 5 Golu Grows a Nose
• Chapter 6 I Want Something in a Cage
• Chapter 7 Chandni
• Chapter 8 The Bear Story
• Chapter 9 A Tiger in the House
• Chapter 10 An Alien Hand

Haryana State Board HBSE 10th Class Social Science Solutions Geography Chapter 6 विनिर्माण उद्योग Textbook Exercise Questions and Answers.

Haryana Board 10th Class Social Science Solutions Geography Chapter 6 विनिर्माण उद्योग

HBSE 10th Class Geography विनिर्माण उद्योग Textbook Questions and Answers

1. बहुवैकल्पिक प्रश्न

(1) निम्न से कौन-सा उद्योग चूना पत्थर को कच्चे माल के रूप में प्रयुक्त करता है?
(क) एल्यूमिनियम
(ख) चीनी
(ग) सीमेंट
(घ) पटसन
उत्तर-
(ग) सीमेंट

(ii) निम्न से कौन-सी एजेंसी सार्वजनिक क्षेत्र में स्टील को बाज़ार में उपलब्ध कराती है?
(क) हेल (HAIL)
(ख) सेल (SAIL)
(ग) टाटा स्टील
(घ) एम एन सी सी (MNCC)
उत्तर-
सेल (SAIL)

(iii) निम्न से कौन-सा उद्योग बॉक्साइट को कच्चे माल के रूप में प्रयोग करता है?
(क) एल्यूमिनियम
(ख) सीमेंट
(ग) पटसन
(घ) स्टील
उत्तर-
(क) एल्यूमिनियम

(iv) निम्न से कौन-सा उद्योग दूरभाष, कंप्यूटर आदि संयंत्र निर्मित करते है?
(क) स्टील
(ख) एल्यूमिनियम
(ग) इलैक्ट्रानिक
(घ) सूचना प्रौद्योगिकी
उत्तर-
(ग) इलैक्ट्रानिक

2. निम्नलिखित प्रश्नों के उत्तर लगभग 30 शब्दों में दीजिए।

(i) विनिर्माण क्या है?
उत्तर-
विनिर्माण-कच्चे पदार्थ को मूल्यवान उत्पादन में परिवर्तित कर अधिक मात्रा में वस्तुओं के उत्पादन को विनिर्माण अथवा वस्तु निर्माण कहलाता है। उदाहरणार्थ-कागज लकड़ी से, चीनी गन्ने से. लोहा-इस्पात लौह-अयस्क से तथा एल्यूमिनियम बॉक्साइड निर्मित होता है।

(ii) उद्योगों की अवस्थिति को प्रभावित करने वाले तीन भौतिक कारक बताएँ।
उत्तर-
उद्योगों की अवस्थिति को प्रभावित करने वाले तीन भौतिक कारक निम्नलिखित है
(क) कच्चे की उपलब्धता
(ख) शक्ति के साधन
(ग) जल तथा जलवायिक दशाएँ विनिर्माण उद्योग की स्थापना हेतु वही स्थान उपयुक्त है जहाँ ये कारक उपलब्ध हो।

(iii) औद्योगिक अवस्थिति को प्रभावित करने वाले तीन मानवीय कारक बताएँ।
उत्तर-
उद्योगों की अवस्थिति को प्रभावित करने वाले तीन मानवीय कारक निम्नलिखित हैं-
(क) काम करने वाले मजदूर
(ख) बाज़ार की उपलब्धता
(ग) धन की आवश्यकता

औद्योगिक प्रक्रिया के प्रारम्भ होने के साथ-साथ नगरीकरण प्रारम्भ होता है। कभी-कभी उद्योग शहरों के समीप या शहरों में लगाये जाते हैं। इस प्रकार औद्योगीकरण तथा नवीकरण साथ-साथ चलते हैं। नगर उद्योगों का बाजार तथा सेवाए उपलब्ध कराते हैं।

(iv) आधारभूत उद्योग क्या है? उदाहरण देकर बताएँ।
उत्तर-
आधारभूत उद्योग-ऐसे उद्योग जो खनिज व ध तुओं को कच्चे माल के रूप में प्रयोग करते हैं, आधारभूत उद्योग कहलाते हैं, उदाहरणार्थ-लोहा तथा इस्पात उद्योग, सीमेंट उद्योग आदि आधारभूत उद्योग है।

3. निम्नलिखित प्रश्नों के उत्तर लगभग 120 शब्दों में दीजिए।

(i) समंवित इस्पात उद्योग मिनी इस्पात उद्योगों से कैसे भिन्न है? इस उद्योग की क्या समस्याएँ हैं? किन सुधारों के अंतर्गत इसकी उत्पादन क्षमता बढ़ी है?
उत्तर-
समन्वित इस्पात अर्थात् संकलित इस्पात उद्योग एक बड़ा संयत्र होता है। जिसमें कच्चे माल को एक स्थान पर इकट्ठा करने से लेकर इस्पात बनाने उसे ढालने और उसे आकार देने तक का प्रत्येक कार्य किया जाता है। जबकि मिनी इस्पात उद्योग छोटे संयत्र है जिनमें विद्युत भट्टी, रद्दी इस्पात व स्पंज आयरन का प्रयोग होता है। इनमें रि-रोलर्स होते हैं जिनमें इस्पात सिल्लियों का प्रयोग के मृदु व मिश्रित इस्पात का उत्पादन करते हैं।

इस्पात उद्योग की संरचना-इस उद्योग में उच्च लागत तथा कोकिंग कोयले की सीमित उपलब्धता, कम श्रमिक ___ उत्पादकता ऊर्जा की अनियमित पूर्ति तथा अविकसित अवसंरचना जैसी अनेक समस्याएँ हैं। .
किये गये सुधार-निजी क्षेत्र में उद्यमियों के प्रत्येक से तथा उदारीकरण व प्रत्यक्ष विदेशी निवेश ने इस्पात उद्योग को प्रोत्साहित किया। इस उद्योग को अधिक स्पर्धावान बनाने हेतु अनुसंधान और विकास के संसाधनों को निश्चित करने की आवश्यकता है।

(ii) उद्योग पर्यावरण को कैसे प्रदूषित करते हैं?
उत्तर-
उद्योग चार प्रकार से पर्यावरण को प्रदूषित करते हैं। ये चार प्रकार निम्नलिखित हैं-

(1) वायु प्रदूषण-अधिक अनुपात में अनैच्छिक गैसों की उपस्थिति( जैसे-सल्फर डाइऑक्साइड तथा कार्बन मोनोऑक्साइड वायु को प्रदूषित करते हैं। रसायन व कागज उद्योग, ईंटों के भट्टे, तेलशोधनशालएँ, प्रगलन उद्योग, जीवाश्म ईंधन दहन और छोटे-बड़े कारखाने प्रदूषण के निममों का उल्लंघन करते हुए धुआँ निष्कासित करते हैं। जहरीली गैसों के रिसाव जैसे दुष्परिणाम होते हैं( जैसे-भोपाल गैस त्रासदी में हुआ था जिसका दुष्प्रभाव लगभग 20 वर्ष व्यतीत के पश्चात् भी आज महसूस किया जा रहा है।

(2) जल प्रदूषण-उद्योगों द्वारा कार्बनिक तथा अकार्बनिक अपशिष्ट पदार्थों को नदी में छोड़ने से जल प्रदूषित होता है। कागज, लुग्दी, रसायन, वस्त्र तथा रंगाई उद्योग, तेल शोधन शालएँ, चमड़ा उद्योग तथा इलेक्ट्रोप्लेटिंग ऐसे उद्योग हैं, जो रंग. अपमार्जक, अम्ल, लवण, सीसा, पारा आदि जल में बहते हैं और जल प्रदूषण का कारण बनते हैं।

(3) तापीय प्रदूषण-कारखानों द्वारा गर्म पानी नदियों में छोड़ने से जलीय जीवन पर बुरा असर पड़ता है। परमाणु ऊर्जा संयंत्रों के अपशिष्ट व परमाणु शस्त्र उत्पादक कारखानों से कैंसर और जन्मजात विकार जैसे रोग फैलते हैं। मलबे के ढेर मिट्टी को अनुपजाऊ बनाते हैं। वर्षा जल के साथ प्रदूषक जमीन में रिसते हुए भूमिगत जल तक पहुँचकर उसे भी प्रदूषित कर देते हैं।

(4) ध्वनि प्रदूषण-औद्योगिक तथा निर्माण कार्य और कारखानों के उपकरणों के द्वारा कोलाहल उत्पन्न होने से ध्वनि प्रदूषण होता है जो श्रवण अक्षमता, हृदय गति, रक्त चाप आदि में वृद्धि करता है।

(iii) उद्योगों द्वारा पर्यावरण निम्नीकरण को कम करने हेतु उठाये गए विभिन्न उपायों की चर्चा करें?
उत्तर-
उद्योगों द्वारा पर्यावरण निम्नीकरण को कम करने हेतु उठाये गये विभिन्न उपाय
(क) विभिन्न प्रक्रियाओं में जल का न्यूनतम उपयोग तथा जल का दो या अधिक उत्तरोत्तर अवस्थाओं में पुनर्चक्रण द्वारा पुन: उपयोग। . (ख) जल की आवश्यकता पूर्ति हेतु वर्षा जल का संग्रहण नदियों व तालाबों में गर्म जल तथा अपशिष्ट पदार्थों को प्रवाहित करने से पूर्व उनका शोधन करना।
औद्योगिक अपशिष्ट का शोधन निम्नलिखित चरणों में किया जा सकता है।

• यान्त्रिक साधनों द्वारा प्राथमिक शोधन। इसके अन्तर्गत अपशिष्ट पदार्थों की छंटाई, उनके छोटे-छोटे टुकड़े करना ढकना तथा तलछट जमाव आदि शामिल है।
• जैविक प्रक्रियाओं द्वारा द्वितीयक शोधन।
• जैविक, रासायनिक तथा भौतिक प्रक्रियाओं द्वारा तृतीयक शोधन। इसमें उपशिष्ट जल को पुनर्चक्रण द्वारा दोबारा प्रयोग योग्य बनाया जाता है।
• जहाँ भूमिगत जल का स्तर कम हैं, वहाँ उद्योगों द्वारा इसके निष्कासन पर कानूनी प्रतिबन्ध होना चाहिए।
• वायु में निलंबित प्रदूषण को कम करने हेतु कारखानों में ऊँची चिमनियाँ, उनमें एलेक्ट्रोस्टैटिक अवक्षेपण, स्क्रबर उपकरण तथा गैसीय प्रदूषक पदार्थों को जड़त्वीय रूप से अलग करने हेतु उपकरण होना चाहिए।
• कारखानों में कोयले की अपेक्षा तेल व गैस के प्रयोग से धुंए के निष्कासन में कमी लायी जा सकती है।

फरीदाबाद में यमुना एक्शन प्लान के
अंतर्गत वाहित मल उपचार संयंत्र

• मशीनों व उपकरणों का उपयोग किया जा सकता है तथा जेनेटरों में साइलेंसर (Silencers) लगाया जा सकता है।
• ऐसी मशीनरी का प्रयोग किया जाए जो ऊर्जा सक्षम हों तथा कम ध्वनि प्रदुषण करे।
• ध्वनि अवशोषित करने वाले उपकरणों के इस्तेमाल के साथ कानों पर शोर नियंत्रण उपकरण भी पहनने चाहिये।

क्रियाकलाप

उद्योगों के संदर्भ में प्रत्येक के लिए एक शब्द दें (संकेतिक अक्षर संख्या कोष्ठक में दी गई है तथा उत्तर अंग्रेजी के शब्दों में हैं)

1. मशीनरी चलाने में प्रयुक्त — (5) POWER
2. कारखानों में काम करने वाले व्यक्ति — (6) WORKER
3. उत्पाद को जहाँ बेचा जाता है — (6) MARKET
4. वह व्यक्ति जो सामान बेचता है — (8) RETAILER
5. वस्तु उत्पादन — (7) PRODUCT
6. निर्माण या उत्पादन — (11) MANUFACTURE
7. भूमि, जल तथा वायु अवनयन — (9) POLLUTION

प्रोजेक्ट कार्य

अपने क्षेत्र के एक कृषि आधारित तथा एक खनिज आधारित उद्योग को चुनें।
(i) ये कच्चे माल के रूप में क्या प्रयोग करते हैं?
(ii) विनिर्माण प्रक्रिया में अन्य निवेश क्या हैं जिनसे परिवहन लागत बढ़ती है।
(iii) क्या ये कारखाने पर्यावरण नियमों का पालन करते हैं?
उत्तर-
विद्यार्थी अपने शिक्षक की सहायता से स्वयं करें।

क्रियाकलाप

निम्न वर्ग पहेली में क्षैतिज अथवा ऊमर्वामार अक्षरों को जोड़ते हुए निम्न प्रश्नों के उत्तर दें।
नोट : पहेली के उत्तर अंग्रेज़ी के शब्दों में हैं।

(i) वस्त्र, चीनी, वनस्पति तेल तथा रोपण उद्योग जो कृषि से कच्चा माल प्राप्त करते हैं, उन्हें कहते हैं.
(ii) चीनी उद्योग में प्रयुक्त होने वाला कच्चा पदार्थ।
(iii) इस रेशे को गोल्डन फाइबर (Golden Fibre) भी कहते हैं।
(iv) लौह-अयस्क, कोकिंग कोयला तथा चूना पत्थर इस उद्योग के प्रमुख कच्चे माल हैं।
(v) छत्तीसगढ़ में स्थित सार्वजनिक क्षेत्र का लोहा-इस्पात उद्योग।
(vi) उत्तर प्रदेश में इस स्थान पर डीज़ल रेलवे इंजन बनाए जाते हैं।

Haryana State Board HBSE 8th Class Science Solutions Chapter 16 Light Textbook Exercise Questions and Answers.

Haryana Board 8th Class Science Solutions Chapter 16 Light

HBSE 8th Class Science Light Textbook Questions and Answers

Question 1.
Suppose you are in a dark room. Can you see object in the room? Can you see objects outside the room. Explain.
Answer:
We cannot see objects in the room because it is a dark room. No light is reflected from the surfaces of the object, so we are not able to see them. But outside the room, the objects can reflect light thus enabling us to see the objects.

Question 2.
Differentiate between regular and diffused reflection. Does diffused reflection mean the failure of the laws of reflection?
Answer:
Following are the differences between a regular reflection and diffused reflection :
Regular Reflection:
(i) It takes place on a smooth surface.
(ii) It has all the reflected rays in parallel.
(iii) Reflected rays are in one direction.

Diffused Reflection:
(i) It takes place on a rough surface.
(ii) Reflected rays are not parallel.
(iii) Reflected rays are scattered in different directions.
Diffused reflection is not due to failure of laws of reflection.

Question 3.
Mention against each of the following whether regular or diffused reflection will take place when a beam of light strikes. Justify your answer in each case.
(a) Polished wooden table
(b) Chalk powder
(c) Cardboard surface
(d) Marble stone with water spread over it
(e) Mirror
(f) Piece of paper
Answer:
(a) A polished wooden table will have regular reflection because its surface is smooth.
(b) A chalk powder will ‘get the diffused reflection because chalk particles are not smooth.
(c) Cardbord surface has minute irregularities on it, so it will have a diffused reflection.
(d) Marble stone with water spread over it will have regular reflection if water is stable but if waves are formed then diffused reflection will take place.
(e) A mirror will reflect light regularly due to its smooth surface.
(f) A piece of paper will have irregular reflection due to minute irregularities on it.

Question 4.
State the laws of reflection.
Answer:
Following are the laws of reflection:
(i) Incident ray, reflected ray and normal drawn at the point of incidence to the reflecting surface always lie in the same plane.
(ii) Angle of incidence is always equal to angle of reflection.

Question 5.
Describe an activity to show that the incident rays, the reflected ray and the normal at the point of incidence lie in the same plane.
Answer:
Take a plane mirror and make it stand with help of block on a plane sheet as shown in figure. Now draw an incident line on it AB. Now see in the mirror and mark the points on the paper, where you feel the line is travelling after

getting reflected from the mirror (P₁ and P₂). Now remove the mirror and mark it as OS and Join the points to make the reflected ray. You will see that, it joins the point of incidence, proving that incident ray is the reflected ray (BC).

Question 6.
Fill in the blanks in the following:
(a) A person 1 m in front of a plane mirror seems to _________ be m away from his image.
(b) If you touch your _________ ear with right hand in front of a plane mirror it will be seen in the mirror that your right ear is touched with .
(c) The size of the pupil becomes _________ when you see in dim light.
(d) Night birds have _________ cones than rods in their eyes.
Answer:
(a) 2 m
(b) left, left
(c) increase
(d) lesser.

Choose the correct option in the Question 7-8.

Question 7.
Angle of incidence is equal to the angle of reflection:
(i) Always
(ii) Sometimes
(iii) Under special conditions
(iv) Never
Answer:
(i) Always.

Question 8.
Image formed by a plane mirror is:
(a) virtual, behind the mirror and enlarged
(b) virtual, behind the mirror and of the same size as the object
(c) teal at the surface of the mirror and enlarged
(d) real, behind the mirror and of the same size as the object.
Answer:
(b) virtual, behind the mirror and of the same size as the object.

Question 9.
Describe the construction of kaleidoscope.
Answer:
Kaleidoscope is made of three strips of plane mirrors. Three strips of plane mirrors of about 15 cm. length and 4 cm. width are taken and arranged as in a prism i.e. in a triangular form.

They are fixed to each other with thick sheet of paper and enclosed in a tube or in a circular carboard. One end of the tube is covered with a round cardboard disc having a hole in the centre. From the opposite open end some pieces of broken bangles or broken coloured glass are put inside the tube. This open end is also closed. When we see inside this tube through the hole in the circular cardboard; we see different patterns of coloured bangle inside it.

Question 10.
Draw a labeled sketch of human eye.
Answer:

Question 11.
Gurmit wanted to perform Activity 16.8 using a laser torch. Her teacher advised her not to do so. Can you explain the basis of the teacher’s advise ?
Answer:
Teacher has advised her to because laser light is harmful for eyes and can cause some permanent damage to eyes when throw directly in eyes.

Question 12.
Explain how you can take care of your eyes?
Answer:
Following precautionary measures can be taken to take care of our eyes:

• We should always wash our eyes with plane cold water atleast three times a day.
• We should not touch our eyes with dirty hands.
• We should never rub our eyes.
• We should not look at Sun directly.
• We should read book, watch T.V., read from black board from a suitable distance.
• Consult an eye specialist if have any irritation, redness in our eyes.

Question 13.
What is the angle of incidence of a ray if the incident and reflected rays is at an angle of 90° to the incident ray?
Answer:
The angle of incidence of the ray will be 45°.

Question 14.
How many images of a candle will be formed if it is placed between two parallel plane mirrors separated by 40 cm?
Answer:
Infinite images will be formed.

Question 15.
Two mirrors meet at right angles. A ray of light is incident on one at an angle of 30° as shown in the figure. Draw the reflected ray from the second mirror.

Answer:

Question 16.
Bhoojo stands at A just on the side of a plane mirror as shown in figure. Can he see himself in the mirror ? Also can he see image of objects situated at P, Q and R?

Answer:
Bhoojo can’t see himself. He can see the images of objects at P and Q.

Question 17.
(a) Find out the position of the image of an object situated at A in the plane mirror, (figure)
(b) Can Paheii at B see this image?
(c) Can Bhoojho at C see this image?
(d) When Paheii moves from B to C, where does the image of A move?

Answer:
(a) Image will be formed at ‘A’.
(b) Yes, Paheii at B can see the image.
(c) No, Boojho can’t see the image at C.
(d) The image will disappear at Paheii moves from B to C.

Extended Learning – Activities and Projects

Question 1.
Make your own mirror. Take a glass strip or glass slab. Clean it and put it on a white sheet of paper. See yourself in the glass. Next put the glass slab on a black sheet of paper. Again look into the glass. In which case do you see yourself better and why?
Answer:
For self attempt.

Question 2.
Make friends with some visually challenged students. Enquire from them how they read and write. Also find out how they are able to recognise objects, hurdles and currency notes.
Answer:
For self attempt.

Question 3.
Meet an eye specialist. Get your eye sight checked and discuss how to take care of your eyes.
Answer:
For self attempt.

Question 4.
Survery your neighbourhood. Find out how many children below the age of 12 years use spectacles. Find out from their parents what, in their view, could be the reason for the weak eyesight of’ their children.
You can read more on this topic on the following websites :
→ www.glenbrook.k 1 2.il.us/gbssci/phys/ mmedia/optics/ifpm.html
→ www.glenbrook.k 1 2 il.us/gbssci/phys/elass/ refln/u131b.html
Answer:
For self attempt.

HBSE 7th Class Science Light Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is sense of sight?
Answer:
The sense which enables us to see object around us is called sense of sight.

Question 2.
What are the sight organs in animals?
Answer:
Eyes.

Question 3.
What is a mirror?
Answer:
Smooth and shiny surface is called a mirror.

Question 4.
What is reflection?
Answer:
Throwing back the incident light by a plane surface is called reflection.

Question 5.
What kind of surfaces reflect light?
Answer:
All surfaces reflect light.

Question 6.
What is incident ray?
Answer:
Beam of light falling on reflecting surface is called incident ray.

Question 7.
What is reflecting ray?
Answer:
Beam of light reflected back by the reflecting surface is called reflected ray.

Question 8.
What is angle of incidence?
Answer:
Angle formed between the incident ray and normal is called angle of incident.

Question 9.
What is angle of reflection?
Answer:
Angle formed between the reflecting ray and normal is called angle of reflection.

Question 19.
State second law of reflection.
Answer:
Angle of incidence and angle of reflection are always same.

Question 11.
What kind of image is formed by a plane mirror?
Answer:
Virtual and erect image.

Question 12.
Where is the image formed by the mirror?
Answer:
Behind the mirror.

Question 13.
What is the size of the image formed?
Answer:
Same as that on the object infront of the mirror.

Question 14.
At what distance is the image formed behind the plane mirror?
Answer:
At the same distance, as is the object infront of the mirror.

Question 15.
What is the phenomenon called where left side appears to be right and vice- versa in a plane mirror?
Answer:
Lateral inversion.

Question 16.
Which surface shows regular reflection?
Answer:
Smooth surface.

Question 17.
Which surface shews diffused reflection?
Answer:
Rough surface.

Question 18.
What kind of reflection will take place from a polished leather shoes top?
Answer:
Regular reflection.

Question 19.
What kind of reflection will take place from the cover of your note-hook?
Answer:
Diffused reflection.

Question 20.
In what kind of reflection does reflected rays go parallelled to each other?
Answer:
Regular reflection.

Question 21.
In what kind of reflection, reflected rays move scattered?
Answer:
In diffused reflection.

Question 22.
floes Moon has its own light?
Answer:
No.

Question 23.
How does moon shine?
Answer:
It reflected light emitted by the Sun.

Question 24.
Name some objects which have light of their own.
Answer:
Sun, fire, flame of candle etc.

Question 25.
What are objects called, which have light of their own?
Answer:
Luminous objects.

Question 26.
How many mirror strips are used to make a Kaleidoscope?
Answer:
Three.

Question 27.
Is white light a pure white light?
Answer:
No.

Question 28.
How many colours constitute a white beam?
Answer:
Seven.

Question 29.
What is the splitting of white light into its constituent colours called?
Answer:
Dispersion.

Question 30.
What is the shape of human eye?
Answer:
It is roughly spherical in shape.

Short Answer Type Questions

Question 1.
What is reflection of light?
Answer:
When a beam of light falls on a surface, it is thrown back by the surface in a different direction in the same medium. This is called reflection of light. Every surface can reflect. The falling beam of light is called incident ray and beam bouncing back is called the reflected ray.

Question 2.
How do we see various objects?
Answer:
We see various objects due to reflection. As we know all surfaces reflect light, when light falls on any object, it reflects the light. The reflected light reaches our eyes and we are enabled to see the objects.

Question 3.
Write the laws of reflection?
Answer:
There are two laws of reflection :
(i) The ray of incidence, ray of reflection and normal drawn at the point of incidence to the reflecting surface lie in the same plane.

(ii) The angle of reflection and angle of incidence are always equal.

Question 4.
What do you mean by following.
(i) Incident ray
(ii) Reflected ray
Answer:
Incident ray : The light ray that strikes any surface is called incident ray.
Reflected ray : The light ray which is thrown away from the surface after reflection in a different direction, is called reflected ray.

Question 5.
What do you mean by angle of incidence and angle of reflection?
Answer:
The angle formed between the incident ray and the normal is called the angle of incidence. The angle of reflection is the angle formed between the reflected ray and the normal. Both these angles are always equal in size.

Question 6.
What is a mirror? What kind of image is formed in a mirror?
Answer:
Any smooth and shining surface can act as mirror. Mirror is a smooth surface which is polished from its back and can form the image of the object which is placed in front of it. The image formed by a mirror is a virtual and erect image and is of same size as that of the object infront of it.

Question 7.
What is dispersion of light?
Answer:
A beam of white light consists of seven colours. When a beam of white light passes through a prism, it splits into its seven constituent colours. The splitting of white light into its seven constituent colours is called dispersion of light.

Question 8.
How many kind of nerve endings are there in our eyes?
Answer:
There are two types of nerve endings in our eyes. The first type of nerve endings are called cones. Cones are sensitive to bright light and other type of nerve endings are called rods. Rods are sensitive to dim light cones are also sensitive to colours.

Question 9.
How do eye muscle adjust themselves to see the near and distant objects?
Or
What is called the accomodation of eyes?
Answer:
The muscles of the eye contract in order to see near objects. When they contract the lens becomes thicker. When the eye has to see a distant object the muscles expand or relax. This makes the lens thinner. This is called accommodation.

Question 10.
What is the cause of dispersion?
Answer:
Different colours of light bend by different angles of refraction. When light enters the glass prism or a drop of water, different colours bend at different angles and become separated to show phenomenon of dispersion.

Question 11.
How do ciliary muscles affect the functioning of eye?
Answer:
Ciliary muscles can contract and relax. Because of this they can change the thickness of eye lens which also changes its focal length. With change in focal length eye lens can make image of near by objects and also far away objects. So power of accommodation of eye is due to the function of the ciliary muscle.

Question 12.
What is a yellow spot in eyes?
Answer:
Yellow spot or macula is a small area, facing the eye lens. It has high concentration of light sensitive nerve endings or cones. The rest of the retina has lesser cones and more number of cells called rods. It is the spot where brightest vision is formed and colour version is formed.

Question 13.
What is the blind spot?
Answer:
It is a region below the yellow spot, where no light sensitive nerve endings are present. It is an area of no vision.

Question 14.
What is Myopia or short sightedness?
Answer:
This is a type of eye defect, in which person can see nearer objects clearly but cannot see the far off objects. This defect is due to thickness of eye lens. Ciliary muscles do not relax enough to make lens thin enough to see distant objects.

Question 15.
What is Hypermetropia or long sightedness?
Answer:
This is a type of an eye defect, in which the person can see far off objects clearly, but cannot see the nearer objects. This defect is due to thinness of the eye lens. The ciliary muscle do not contract enough to make the lens see nearer objects.

Question 16.
What is cataract? How can it be corrected?
Answer:
During old age, the eye sight becomes blurred. It happens because the lens of the eye becomes opaque and milky. When the vision becomes cloudy the person is said to have cataract. It is possible to treat this temporary loss of vision by removing the opaque lens and, a new artificial lens is inserted by minor and simpe operation.

Question 17.
Write any three safety measures to protect our eyes.
Answer:

• We should not rub our eyes.
• We should wash our eyes many times a day.
• We should not look at sun or other powerful lights directly.

Question 18.
What is Braille system?
Answer:
Braille is based on code of one to six dots which are raised. Each dot has a position. These dots make up letters of alphabet, number and all other things done in print. Any language can be read through the codes of the braille by touching the dots.

Long Answer Type Questions

Question 1.
What is reflection of light? State laws of reflection.
Answer:
Reflection of light is throwing back of light by any object. When a beam of light falls on some surface, the surface throws that beam away in different direction. This is called reflection of light. Following are the laws of reflection:

(a) When a ray of light falls on a reflecting surface, it is reflected in such a way that the angle of incidence is equal to the angle of reflection i.e. ∠i = ∠r.

(b) The incident ray, the normal and the reflected ray, all lie in the same plane.

Question 2.
What are the characteristics of image formed with a plane mirror?
Answer:
Plane mirror is a shiny, polished surface. When any object is placed in front of the mirror, an image is formed. Following are the characteristics of the image formed by a plane mirror:

• Image formed on a plane mirror cannot be taken on a screen, such image is called a virtual image.
• Image formed on a plane mirror is erect.
• It is laterally inverted i.e. left hand of the object appears as the right hand.
• Image formed is as far behind as the object is in front of it.

Question 3.
What are the uses of a plane mirror?
Answer:

• We use a plane mirror to see our reflections in it, at our homes.
• Plane mirrors are used to reflect light on a particular object.
• Plane mirrors are used for signalling by scouts and army.
• They are used to form multiple images in show windows.
• Plane mirror is used to reflect sun rays in appliances like solar cooker etc.
• Toys like Kaleidoscope are made on the concept of multiple reflection. Navy use periscopes based on concept of multiple reflection for spying in sea.

Question 4.
Describe how does human eye work?
Answer:
The light reflected by objects enter our eyes through cornea. That is why cornea is called window to the world. Lens focuses the image of the object on the retina. Retina converts these optical images into optical pulses. These optical pulses are then sent to brain through optical nerves. The amount of light entering the eye through cornea is controlled by Iris. It expands when light is bright and thus enables the pupil to enter controlled amount of light to enter the eye. In dark it contracts and increases the size of pupil to allow more light to enter the eye.

The retina forms a small and inverted image of the object. The brain interprets it and forms the erect and correct sized image.

Question 5.
Write various measures to save our eyes.
Answer:
Eyes are a precious gift of God. We should take proper care of our eyes and protect them from injury. Following measures should be taken for healthy eyes :

• We should wash our eyes with cold water everyday and wipe them with clean and soft cloth.
• We should never rub our eyes. If some particle enters our eyes, we should wash our eyes with cold water.
• We should always read in proper light.
• In case of any injury or other problems related to eyes, we should avoid self medication and immediately consult an eye specialist.

Question 6.
What is blindness? How many types of blindness do we know about?
Answer:
A person is said to be blind or visually impaired when he or she is imable to see. Blindness is of two types:
Curable Blindness : When cornea becomes opaque or the lens becomes opaque the sight of the person becomes decreased. This is called a temporary or curable blindness. In this case the person is operated upon and sight is resorted. An artificial lens is inserted in place of opaque lens and the opaque cornea is replaced with a healthy donated cornea.

Permanent Blindness : In this type of blindness image formed by cornea is not transferred to brain and this type of blindness cannot be cured.

Pollution of Air and Water Class 8 HBSE Notes

• We see all the things around us only due to sense of sight.
• Eyes are our organs of sight, which enables us to see objects around us.
• It is the light which enables our eyes to see the objects. Without light our eyes cannot sense anything.
• Any polished or shiny surface acts as a mirror. It can change the direction of light.
• Light is reflected from all the surfaces.
• When a beam of light falls on a surface, it throws back the light to same medium. This phenomenon is called reflection of light.
• The beam of light falling on the plane surface is called the incident ray.
• The beam of light thrown back by the reflecting surface is called the reflected ray.
• The line drawn between the point where the incident ray and reflected ray meet is called the normal.
• The angle between the normal and the incident ray is called angle of incidence.
• The angle between the normal and the reflected ray is called the angle of reflection.
• The angle of incidence and the angle of reflection are equal.
• Incident ray, reflected ray and the normal drawn at the point of incidence to reflecting surface lie in the same plane.
• Above two points are called laws of reflection.
• Light falling on a smooth surface is reflected regularly.
• Irregular or diffused reflection takes place on rough surface.
• In mirror the right appears as left and left as right. This is called lateral inversion.
• Two mirrors inclined to each other at different angles, give multiple images.
• White light consists of seven colours called spectrum.
• Splitting of white light into its constituting seven colours is callled dispersion.
• Our eyes have different parts which perform different functions to enable us to see the objects.
• Visually challanged persons can read and write using Braille system.

Haryana State Board HBSE 7th Class Maths Solutions Chapter 2 भिन्न एवं दशमलव Ex 2.2 Textbook Exercise Questions and Answers.

Haryana Board 7th Class Maths Solutions Chapter 2 भिन्न एवं दशमलव Ex 2.2

प्रश्न 1.
(a) से (d) तक के रेखाचित्रों में निम्नलिखित को कौन दर्शाता है :

हल :
(i) (d),
(ii) (b),
(iii) (a),
(iv) (c)

प्रश्न 2.
(a) से (c) तक कुछ चित्र दिए हुए हैं। बताइए उनमें से कौन निम्नलिखित को दर्शाता है :

हल :
(i) (c),
(ii) (a),
(iii) (b)

प्रश्न 3.
गुणा करके न्यूनतम रूप में लिखिए और मिश्रित भिन्न में व्यक्त कीजिए :
हल :
(i) 7 × \(\frac{3}{5}=\frac{7 \times 3}{5}=\frac{21}{5}=4 \frac{1}{5}\)

प्रश्न 4.
छायाँकित कीजिए :
(i) बक्सा (a) के वृत्तों का \(\frac {1}{2}\) भाग
(ii) बक्सा (b) के त्रिभुजों का \(\frac {2}{3}\) भाग
(iii) बक्सा (c) के वर्गों का \(\frac {3}{5}\) भाग

हल :

प्रश्न 5.
ज्ञात कीजिए :
हल :
(a) (i) 24 का \(\frac {1}{2}\) = \(\frac {1}{2}\) × 24 = 12
(ii) 46 का \(\frac {1}{2}\) = \(\frac {1}{2}\) × 46 = 23

(b) (i) 18 का \(\frac {2}{3}\) = \(\frac {2}{3}\) × 18 = 2 × 6 = 12
(ii) 27 का \(\frac {2}{3}\) = \(\frac {2}{3}\) × 27 = 2 × 9 = 18

(c) (i) 16 का \(\frac {3}{4}\) = \(\frac {3}{4}\) × 16 = 3 × 4 = 12
(ii) 36 का \(\frac {3}{4}\) = \(\frac {3}{4}\) × 36 = 3 × 9 = 27

(d) (i) 20 का \(\frac {4}{5}\) = \(\frac {4}{5}\) × 20 = 4 × 4 = 16
(ii) 35 का \(\frac {4}{5}\) = \(\frac {4}{5}\) × 35 = 4 × 7 = 28

प्रश्न 6.
गुणा कीजिए और मिश्रित भिन्न के रूप में व्यक्त कीजिए:
हल :

प्रश्न 7.
ज्ञात कीजिए :
हल :

प्रश्न 8.
विद्या और प्रताप पिकनिक पर गए। उनकी माँ ने उन्हें 5 लीटर पानी वाली एक बोतल दी। विद्या ने कुल पानी का \(\frac {2}{5}\) उपयोग किया। शेष पानी प्रताप ने पिया।
(i) विद्या ने कितना पानी पिया?
(ii) पानी की कुल मात्रा का कितना भिन्न (fraction) प्रताप ने पिया?
हल :
कुल पानी = 5 लीटर
(i) विद्या ने पानी पिया = 5 लीटर का \(\frac {2}{5}\) भाग
= (\(\frac {2}{5}\) × 5) लीटर
= 2 लीटर उत्तर

(ii) प्रताप द्वारा पिया गया पानी का भिन्न
= 1 – \(\frac{2}{5}=\frac{5}{5}-\frac{2}{5}\)
= \(\frac{5-2}{5}=\frac{3}{5}\) उत्तर

Haryana State Board HBSE 10th Class Maths Solutions Chapter 6 त्रिभुज Ex 6.3 Textbook Exercise Questions and Answers.

Haryana Board 10th Class Maths Solutions Chapter 6 त्रिभुज Exercise 6.3

नोट : यह प्रश्नावली निम्नलिखित तीन प्रमेय पर आधारित है
प्रमेय 6.3 : यदि दो त्रिभुजों में, संगत कोण बराबर हों, तो उनकी संगत भुजाएँ एक ही अनुपात में (समानुपाती) होती हैं और इसीलिए ये त्रिभुज समरूप होते हैं।

हल :
दिया है : ΔABC और ΔDEF में ∠A = ∠D, ∠B = ∠E तथा ∠C = ∠F है।
सिद्ध करना है : ΔABC ~ ΔDEF
रचना : ΔDEF में DP = AB तथा DQ =AC काटिए और P व Q को मिलाइए।
उपपत्ति : ΔABC और ΔDPQ में,
AB = DP (रचना से)
∠A = ∠D (दिया है)
AC = DQ (रचना से)
∴ ΔABC ≅ ΔDPQ (भुजा-कोण-भुजा सर्वांगसमता)
∠B = ∠DPQ
∠B = ∠E= ∠DEF
∴ ∠DPQ = ∠DEF
परंतु ये संगतकोण हैं।
PQ || EF

अतः ΔABC ≅ ΔDPQ (इति सिद्धम)

प्रमेय 6.4 : यदि दो त्रिभुजों में एक त्रिभुज की भुजाएँ दूसरे त्रिभुज की भुजाओं के समानुपाती (अर्थात् एक ही अनुपात में) हों, तो इनके संगत कोण बराबर होते हैं और इसीलिए दोनों त्रिभुज समरूप होते हैं।
हल :

दिया है : ΔABC और ΔDEF में,
\(\frac{\mathrm{AB}}{\mathrm{DE}}=\frac{\mathrm{BC}}{\mathrm{EF}}=\frac{\mathrm{CA}}{\mathrm{FD}}\) है।
सिद्ध करना है : ΔABC ~ ΔDEF
रचना : ΔDEF में DP = AB तथा DQ = AC काटिए। Pव Q को मिलाइए।
उपपत्ति : दिया है,
\(\frac{\mathrm{AB}}{\mathrm{DE}}=\frac{\mathrm{AC}}{\mathrm{DF}}\)
\(\frac{\mathrm{DP}}{\mathrm{DE}}=\frac{\mathrm{DQ}}{\mathrm{DF}}\) [∵ AB = DP व AC = DQ (रचना से)]
[∵ΔDEF में रेखा PQ, भुजाओं DE व DF को समानुपात में काटती है]
∠P = ∠E व ∠Q = ∠F (संगत कोण युग्म)
अब ΔDPQ व ΔDEF में,
∠P = ∠E a ∠Q = ∠F
ΔDPQ ~ ΔDEF

PQ = BC
अतः ΔABC व ΔDPQ
AB = DP, AC = DQ व BC = PQ
ΔABC ≅ ΔDPQ ———— (ii) (भुजा-भुजा-भुजा सर्वांगसमता)
समीकरण (i) व (ii) की तुलना से, . ΔABC ~ ΔDEF (इति सिद्धम)

प्रमेय 6.5 : यदि एक त्रिभुज का एक कोण दूसरे त्रिभुज के एक कोण के बराबर हो तथा इन कोणों को अंतर्गत करने वाली भुजाएँ समानुपाती हों, तो दोनों त्रिभुज समरूप होते हैं।
हल :

दिया है : ΔABC और ΔDEF में \(\frac{\mathrm{AB}}{\mathrm{DE}}=\frac{\mathrm{AC}}{\mathrm{DF}}\) तथा ∠A = ∠D है।
सिद्ध करना है : ΔABC ~ ΔDEF
रचना : ΔDEF में DP = AB तथा DQ = AC काटिए B और P व Q को मिलाइए।
उपपत्ति : \frac{\mathrm{AB}}{\mathrm{DE}}=\frac{\mathrm{AC}}{\mathrm{DF}}ABC और ΔDPQ में,
AB = DP, AC = DQ (रचना से)
∠A = ∠D (दिया है)
ΔABC ≅ ΔDPQ (भुजा-कोण-भुजा सर्वांगसमता)
ΔABC ~ ΔDPQ … (i) (दिया है)
\(\frac{\mathrm{DP}}{\mathrm{DE}}=\frac{\mathrm{DQ}}{\mathrm{DF}}\) [∵ AB = DP व AC = DQ (रचना से)]
PQ || EF (थेल्स प्रमेय के विलोम से)
∠P = ∠E a ∠Q = ∠F (संगत कोण युग्म)
ΔDPQ तथा ΔDEF में,
∠D = ∠D, ∠P = ∠E व ∠Q = ∠F
ΔDPQ ~ ΔDEF (कोण-कोण-कोण समरूपता) …..(ii)
समीकरण (i) व (ii) की तुलना से,
ΔABC ~ ΔDEF (इति सिद्धम)

प्रश्न 1.
बताइए कि निम्नांकित आकृति में दिए त्रिभुजों के युग्मों में से कौन-कौन से युग्म समरूप हैं। उस समरूपता कसौटी को लिखिए जिसका प्रयोग आपने उत्तर देने में किया है तथा साथ ही समरूप त्रिभुजों को सांकेतिक रूप में व्यक्त कीजिए।

हल :
(i) यहाँ पर ΔABC और ΔPQR में,
∠A = ∠P
∠B = ∠Q
व ∠c = ∠R
ΔABC ~ ΔPQR (कोण-कोण-कोण समरूपता)

(ii) यहाँ पर ΔABC और ΔQRP में,

(iii) यहाँ पर ΔMPL और ΔDEF में,

इसलिए ΔMPL और ΔDEF समरूप नहीं है क्योंकि ये समरूपता की भुजा-भुजा-भुजा कसौटी को सत्यापित नहीं करती।

(iv) यहाँ पर ΔMNL और ΔQPR में,

इसलिए ΔMNL ~ ΔQPR भुजा-कोण-भुजा समरूपता से)

(v) यहाँ पर ΔABC और ΔDEF में,
\(\frac{\mathrm{AB}}{\mathrm{DF}}=\frac{2.5}{5}=\frac{1}{2}\)
\(\frac{\mathrm{BC}}{\mathrm{EF}}=\frac{3}{6}=\frac{1}{2}\)
परंतु ∠B ≠ ∠F (∵ ∠B दिया नहीं है।)
अतः ΔABC और ΔDEF समरूप नहीं है।

(vi) यहाँ पर ΔDEF और ΔPQR में,
∠P = 180° – (∠Q+ ∠R)
= 180° – (80° + 30°) = 70°
∠F = 180° – (∠D+ ∠E)
= 180° – (70° + 80°) = 30°
∠D = ∠P (प्रत्येक 70°)
∠E = ∠Q व (प्रत्येक 80°)
∠F = ∠R. (प्रत्येक 30°)
ΔDEF ~ ΔPQR (कोण-कोण-कोण समरूपता से)

प्रश्न 2.
संलग्न आकृति में, ΔODC ~ ΔOBA, ∠BOC = 125° और ∠CDO = 70° है। ∠DOC, ∠DCO और ∠OAB ज्ञात कीजिए।
हल :
यहाँ पर, ∠BOC = 125°
व ∠CDO = 70°

∠DOC + ∠BOC = 180°
∠DOC + 125° := 180°
∠DOC = 180° – 125° = 55°
अब ΔDOC में, ∠DOC + ∠CDO + ∠DCO = 180°
55° + 70° + ∠DCO = 180°
∠DCO = 180° – 125° = 55°
परंतु ΔODC ~ ΔOBA (दिया है)
इसलिए ∠OAB = ∠DCO
= 55°
अतः ∠DOC = 55°, ∠DCO = 55° व ∠OAB = 55° उत्तर

प्रश्न 3.
समलंब ABCD, जिसमें AB ||DC है, के विकर्ण AC और BD परस्पर 0 पर प्रतिच्छेद करते हैं। दो त्रिभुजों की समरूपता कसौटी का प्रयोग करते हुए, दर्शाइए की \(\frac{O A}{O C}=\frac{O B}{O D}\) है

हल :
दिया है : ABCD एक समलंब है जिसमें AB || DC है। इसके विकर्ण AC और BD, O पर मिलते हैं।
सिद्ध करना है : \(\frac{O A}{O C}=\frac{O B}{O D}\)
प्रमाण : ΔOAB और ΔODC में,
∠AOB = ∠COD (शीर्षाभिमुख कोण)
∠OAB = ∠OCD (एकांतर कोण)
∠OBA = ∠ODC (एकांतर कोण)
ΔOAB ~ ΔODC (कोण-कोण-कोण समरूपता नियम से)
\(\frac{\mathrm{OA}}{\mathrm{OC}}=\frac{\mathrm{OB}}{\mathrm{OD}}\) (समरूप त्रिभुजों के संगत भागों का अनुपात) [इति सिद्धम]

प्रश्न 4.
संलग्न आकृति में, \(\frac{Q R}{Q S}=\frac{Q T}{P R}\) तथा ∠1 = ∠2 है। दर्शाइए कि ΔPQS ~ ΔTQR है।

हल :
यहाँ पर
\(\frac{\mathrm{QR}}{\mathrm{QS}}=\frac{\mathrm{QT}}{\mathrm{PR}}\) (दिया है)
\(\frac{\mathrm{PR}}{\mathrm{QS}}=\frac{\mathrm{QT}}{\mathrm{QR}}\) …(i)
तथा ∠1 = ∠2 (दिया है)
PR = PQ …. (ii) [ ∵ ΔPQR में समान कोणों की सम्मुख भुजाएँ]
समीकरण (i) व (ii) की तुलना से,
\(\frac{\mathrm{PQ}}{\mathrm{QS}}=\frac{\mathrm{QT}}{\mathrm{QR}}\)
\(\frac{\mathrm{PQ}}{\mathrm{QT}}=\frac{\mathrm{QS}}{\mathrm{QR}}\)
अब ΔPQS और ΔTQR में,
\(\frac{\mathrm{PQ}}{\mathrm{QT}}=\frac{\mathrm{QS}}{\mathrm{QR}}\)
∠PQS = ∠TQR
ΔPQS ~ ΔTQR (भुजा-कोण-भुजा समरूपता से)

प्रश्न 5.
ΔPQR की भुजाओं PR और QR पर क्रमशः बिंदु S और T इस प्रकार स्थित हैं कि ∠P= ∠RTS है। दर्शाइए कि ΔRPQ ~ΔRTS है।

हल :
दिया है : ΔPQR की भुजाओं PR और QR पर क्रमशः बिंदु S और T इस प्रकार है कि ∠P= ∠RTS
सिद्ध करना है: ΔRPQ ~ ΔRTS
प्रमाण : ΔRPQ और ΔRTS में, .
∠R = ∠R (उभयनिष्ठ)
∠P = ∠RTS (दिया है)
∴ कोण-कोण समरूपता गुणधर्म से,
ΔRPQ ~ ΔRTS

प्रश्न 6.
संलग्न आकृति में, यदि ΔABE ≅ ΔACD है, तो दर्शाइए कि ΔADE ~ ΔABC है।

हल :
दिया है : ΔABE ≅ ΔACD
सिद्ध करना है : ΔADE ~ ΔABC
प्रमाण : ΔABE ≅ ΔACD (दिया है)
AB = AC
AE = AD

अब ΔADE और ΔABC में,
\(\frac{\mathrm{AB}}{\mathrm{AC}}=\frac{\mathrm{AD}}{\mathrm{AE}}\)
∠BAC = ∠DAE (उभयनिष्ठ)
ΔADE ~ ΔABC (भुजा-कोण-भुजा समरूपता से) (इति सिद्धम)

प्रश्न 7.
संलग्न आकृति में, ΔABC के शीर्षलंब AD और CE परस्पर बिंदु Pपर प्रतिच्छेद करते हैं। दर्शाइए कि-
(i) ΔAEP ~ ΔCDP
(ii) ΔABD ~ ΔCBE
(iii) ΔAEP ~ ΔADB
(iv) ΔPDC ~ ΔBEC

हल :
दिया है : ΔABC के दो शीर्षलंब AD व CE हैं अर्थात् AD ⊥ BC व CE ⊥ AB हैं।

(i) सिद्ध करना है : ΔAEP ~ ΔCDP
प्रमाण : ΔAEP और ΔCDP में,
∠AEP = ∠CDP (प्रत्येक 90°)
∠APE = ∠CPD (शीर्षाभिमुख कोण)
ΔAEP ~ ΔCDP (कोण-कोण समरूपता नियम से) [इति सिद्धम]

(ii) सिद्ध करना है : ΔABD ~ ΔCBE
प्रमाण : ΔABD और ΔCBE में
∠ADB = ∠CEB (प्रत्येक 90°)
∠ABD = ∠CBE (उभयनिष्ठ)
ΔABD ~ ΔCBE (कोण-कोण समरूपता नियम से) [इति सिद्धम]

(iii) सिद्ध करना है : ΔAEP ~ ΔADB
प्रमाण : ΔAEP और ΔADB में,
∠AEP = ∠ADB (प्रत्येक 90°)
∠EAP = ∠DAB (उभयनिष्ठ)
ΔAEP ~ ΔADB (कोण-कोण समरूपता नियम से) [इति सिद्धम]

(iv) सिद्ध करना है : ΔPDC ~ ΔBEC
प्रमाण : ΔPDC और ΔBEC में
∠PDC = ∠EEC (प्रत्येक 90°)
∠PCD = ∠ECB (उभयनिष्ठ)
ΔPDC ~ ΔBEC (कोण-कोण समरूपता नियम से) [इति सिद्धम]

प्रश्न 8.
समांतर चतुर्भुज ABCD की बढ़ाई गई भुजा AD पर स्थित E एक बिंदु है तथा BE भुजा CD को F पर प्रतिच्छेद करती है। दर्शाइए कि ΔABE ~ ΔCFB है।
हल :
दिया है : ABCD एक समांतर चतुर्भुज है, जिसकी भुजा AD को E तक बढ़ाया गया है तथा BE को मिलाने पर BE भुजा CD को F बिंदु पर प्रतिच्छेदित करती है।

सिद्ध करना है : ΔABE ~ ΔCFB
प्रमाण : ΔABE और ΔCFB में,
∠A = ∠C (समांतर चतुर्भुज के सम्मुख कोण)
∠AEB = ∠CBF (एकांतर कोण)
ΔABE ~ ΔCFB (कोण-कोण समरूपता नियम से) [इति सिद्धम]

प्रश्न 9.
संलग्न आकृति में, ABC और AMPदो समकोण त्रिभुज हैं, जिनके कोण Bऔर M समकोण हैं। सिद्ध कीजिए कि
(i) ΔABC ~ ΔAMP
(ii) \(\frac{\mathbf{C A}}{\mathbf{P A}}=\frac{\mathbf{B C}}{\mathbf{M P}}\)

हल :
दिया है-दो समकोण ΔABC व ΔAMP में ∠ABC= 90° व ∠AMP = 90°
(i) सिद्ध करना है-ΔABC ~ ΔAMP
प्रमाण-ΔABC और ΔAMP में,
∠ABC = ∠AMP (प्रत्येक 90°)
∠BAC = ∠MAP (उभयनिष्ठ)
ΔABC ~ ΔAMP (कोण-कोण समरूपता नियम से) (इति सिद्धम)

(ii) सिद्ध करना है \(\frac{\mathbf{C A}}{\mathbf{P A}}=\frac{\mathbf{B C}}{\mathbf{M P}}\)
प्रमाण-ΔABC और ΔAMP में,
∠ABC = ∠AMP (प्रत्येक 90°)
∠BAC = ∠MAP
(उभयनिष्ठ) ΔABC ~ ΔAMP (कोण-कोण समरूपता नियम से)
अतः \(\frac{\mathrm{CA}}{\mathrm{PA}}=\frac{\mathrm{BC}}{\mathrm{MP}}\)
(समरूप त्रिभुजों के संगत भाग) (इति सिद्धम)

प्रश्न 10.
CD और GH क्रमशः ∠ACB और ∠EGF के ऐसे समद्विभाजक हैं कि बिंदु D और Hक्रमशः ΔABC और ΔFEG की भुजाओं AB और FE पर स्थित हैं। यदि ΔABC ~ ΔFEG है, तो दर्शाइए कि
(i) GH FG
(ii) ΔDCB ~ ΔHGE
(iii) ΔDCA ~ ΔHGF
हल :
दिया है : दो त्रिभुज ABC और FEG में CD और GH क्रमशः ∠ACB और ∠EGF के समद्विभाजक हैं तथा ΔABC ~ ΔFEG हैं।

(i) सिद्ध करना है : \(\frac{\mathrm{CD}}{\mathrm{GH}}=\frac{\mathrm{AC}}{\mathrm{FG}}\)
प्रमाण : ΔADC और ΔFHG में,
∠A = ∠F [∵ ΔABC ~ ΔFEG]
तथा∠C = ∠G [∵ ΔABC ~ ΔFEG]
या \(\frac{1}{2}\) ∠C = \(\frac{1}{2}\)∠G
या ∠ACD = ∠FGH
ΔADC ~ ΔFHG (कोण-कोण समरूपता नियम से)
\(\frac{\mathrm{CD}}{\mathrm{GH}}=\frac{\mathrm{AC}}{\mathrm{FG}}\)(सर्वांगसम त्रिभुजों के संगत भाग) [इति सिद्धम]

(ii) सिद्ध करना है : ΔDCB ~ ΔHGE
प्रमाण : ΔDCB और ΔHGE में,
∴ ∠DBC = ∠HEG [ ∵ ΔABC ~ ΔFEG]
तथा ∠C = ∠G [ ∵ ΔABC ~ ΔFEG]
या \(\frac{1}{2}\)∠C = ∠G\(\frac{1}{2}\)
या ∠BCD = ∠EGH
∴ ΔDCB ~ ΔHGE (कोण-कोण समरूपता नियम से) [इति सिद्धम]

(iii) सिद्ध करना है : ΔDCA ~ ΔHGF
प्रमाण : ΔDCA और ΔHGF में,
∠A = ∠F [∵ ΔABC – ΔFEG] |
तथा ∠C = ∠G [∵ ΔABC – ΔFEG]
या \(\frac{1}{2}\)∠C = ∠G\(\frac{1}{2}\)
या ∠ACD = ∠FGH
∴ ΔDCA ~ ΔHGF(कोण-कोण समरूपता नियम से) [इति सिद्धमा)

प्रश्न 11.
संलग्न आकृति में, AB = AC वाले, एक समद्विबाहु त्रिभुज ABC की बढ़ाई गई भुजा CB पर स्थित E एक बिंदु है। यदि AD ⊥ BC और EF ⊥ AC है तो सिद्ध कीजिए कि ΔABD ~ΔECF है।

हल :
दिया है : एक समद्विबाहु ΔABC जिसमें AB = AC है। इसकी बढ़ाई गई भुजा CB पर E कोई बिंदु है। AD ⊥ BC तथा EF ⊥ AC है।
सिद्ध करना है : ΔABD ~ ΔECF
प्रमाण : ΔABD और ΔECF में,
∠B = ∠C [∵ AB = AC दिया है]
∠ADB = ∠EFC (प्रत्येक 90°)
ΔABD ~ ΔECF (कोण-कोण समरूपता नियम से) [इति सिद्धम]

प्रश्न 12.
एक त्रिभुज ABC की भुजाएँ AB और BC तथा माध्यिका AD एक अन्य त्रिभुज PQR की क्रमशः भुजाओं PQ और QR तथा माध्यिका PM के समानुपाती हैं (देखिए संलग्न आकृति)। दर्शाइए कि ΔABC ~ ΔPQR है।

हल :
दिया है : दो त्रिभुजों ABC और PQR में AD व PM क्रमशः भुजाओं BC और QR की माध्यिकाएँ हैं तथा
\(\frac{\mathrm{AB}}{\mathrm{PQ}}=\frac{\mathrm{BC}}{\mathrm{QR}}=\frac{\mathrm{AD}}{\mathrm{PM}}\)
सिद्ध करना है : ΔABC ~ ΔPQR
प्रमाण : क्योंकि AD भुजा BC की माध्यिका है।
∴ BD = \(\frac{1}{2}\)BC
इसी प्रकार QM = \(\frac{1}{2}\)QR

ΔABD ~ ΔPQM(भुजा-भुजा-भुजा समरूपता से)
∠B = ∠Q (समरूप त्रिभुजों के संगत भाग)
अब ΔABC व ΔPQR में
\(\frac{\mathrm{AB}}{\mathrm{PQ}}=\frac{\mathrm{BC}}{\mathrm{QR}}\) व ∠B = ∠Q
ΔABC ~ ΔPQR (भुजा-कोण-भुजा समरूपता से) [इति सिद्धम]

प्रश्न 13.
एक त्रिभुज ABC की भुजा BC पर एक बिंदु D इस प्रकार स्थित है कि ∠ADC = ∠BAC है। दर्शाइए कि CA² =CB.CD है।
हल : दिया है : ΔABC की भुजा BC पर D कोई ऐसा बिंदु है कि ∠ADC = ∠BAC
सिद्ध करना है : CA² = CB.CD

प्रमाण : ΔABC और ΔADC में,
∠BAC = ∠ADC (दिया है)
∠BCA = ∠DCA (उभयनिष्ठ)
तथा ∠ABC = ∠DAC (त्रिभुज का तीसरा कोण)
अतः ΔABC ~ ΔADC (कोण-कोण समरूपता से)
\(\frac{\mathrm{CA}}{\mathrm{CD}}=\frac{\mathrm{CB}}{\mathrm{CA}}\) ( ∵ समरूप त्रिभुजों के संगत भाग समान अनुपाती होते हैं।)
CA² = CB.CD इति सिद्धमा

प्रश्न 14.
एक त्रिभुज ABC की भुजाएँ AB और AC तथा माध्यिका AD एक अन्य त्रिभुज की भुजाओं PQ और PR तथा माध्यिका PM के क्रमशः समानुपाती हैं। दर्शाइए कि ΔABC ~ΔPQR है।
हल :
दिया है : दो त्रिभुजों ABC और PQR में AD व PM क्रमशः भुजाओं BC और QR की माध्यिकाएँ हैं तथा
\(\frac{A B}{P Q}=\frac{A C}{P R}=\frac{A D}{P M}\)

सिद्ध करना है : ΔABC ~ ΔPQR
रचना : D से DE || AB तथा M से MN || PQ खींचिए।
प्रमाण : क्योंकि D, BC का मध्य बिंदु है तथा DE || AB (रचना से)
E,AC का मध्य-बिंदु है।
अर्थात् DE = \(\frac{1}{2}\) AB
इसी प्रकार MN =\(\frac{1}{2}\) PQ

ΔADE ~ ΔPMN (भुजा-भुजा-भुजा समरूपता नियम से)
∠DAE = ∠MPN
∠DAC = CMPR …..(ii)
इसी प्रकार ∠DAB = ∠MPQ …… (ii)
समीकरण (i) व (ii) से,
∠DAC + ∠DAB = ∠MPR + ∠MPQ
∠BAC = ∠QPR
अब ΔABC और ΔPQR में,
\(\frac{A B}{P Q}=\frac{A C}{P R}\) तथा ∠BAC = ∠QPR
∴ ΔABC ~ ΔPOR (भुजा-कोण-भुजा समरूपता से) [इति सिद्धमा

प्रश्न 15.
लंबाई 6m वाले एक ऊर्ध्वाधर स्तंभ की भूमि पर छाया की लंबाई 4m है, जबकि उसी समय एक मीनार की छाया की लंबाई 28m है। मीनार की ऊँचाई ज्ञात कीजिए।
हल :

दिया है : एक स्तंभ PM = 6m जिसकी छाया OM = 4m है।
सिद्ध करना है : एक मीनार NS की ऊँचाई (माना xm) जिसकी छाया OS की लंबाई 28m है।
प्रमाण : ΔOPM व ΔONS में,
∠O = ∠O (उभयनिष्ठ)
∠OMP = ∠OSN (प्रत्येक 90°)
∴ ΔOMP ~ ΔONS (कोण-कोण समरूपता)
\(\frac{P M}{N S}=\frac{O M}{O S}\)
\(\frac{6}{x}=\frac{4}{28}\)
x = \(\) = 42
अतः मीनार की ऊँचाई = 42m

प्रश्न 16.
AD और PM त्रिभुजों ABC और PQR की क्रमशः माध्यिकाएँ हैं, जबकि AABC ~ APQR है। सिद्ध कीजिए कि \(\frac{\mathrm{AB}}{\mathrm{PQ}}=\frac{\mathrm{AD}}{\mathrm{PM}}\) है।
हल :

दिया है : AD और PM त्रिभुजों ABC व PQR की क्रमशः माध्यिकाएँ हैं जहाँ ΔABC ~ ΔPQR है।
सिद्ध करना है : \(\frac{\mathrm{AB}}{\mathrm{PQ}}=\frac{\mathrm{AD}}{\mathrm{PM}}\)
प्रमाण : क्योंकि ΔABC ~ ΔPQR (दिया है)।

Haryana State Board HBSE 7th Class Maths Solutions Chapter 2 भिन्न एवं दशमलव Ex 2.1 Textbook Exercise Questions and Answers.

Haryana Board 7th Class Maths Solutions Chapter 2 भिन्न एवं दशमलव Ex 2.1

प्रश्न 1.
हल कीजिए :

हल :

प्रश्न 2.
निम्नलिखित को अवरोही क्रम में रखिए :
(i) \(\frac{2}{9}, \frac{2}{3}, \frac{8}{21}\)
(ii) \(\frac{1}{5}, \frac{3}{7}, \frac{7}{10}\)
हल :
सबसे पहले इन्हें तुल्य भिन्न में परिवर्तित करेंगे। इसके लिए पहले इनके हरों का ल.स. ज्ञात करते हैं।

प्रश्न 3.
एक ‘जादुई वर्ग’ में प्रत्येक पंक्ति, प्रत्येक स्तम्भ एवं प्रत्येक विकर्ण की संख्याओं का योग समान होता है। क्या यह एक जादुई वर्ग है?

हल :


इस प्रकार, प्रत्येक पंक्ति, स्तम्भ तथा विकर्ण के योग समान हैं।
अतः यह एक जादुई वर्ग है।

प्रश्न 4.
एक आयताकार कागज की लम्बाई 12\(\frac {1}{2}\) cm और चौड़ाई 10\(\frac {2}{3}\) cm है। कागज का परिमाप ज्ञात कीजिए।
हल :
आयत का परिमाप = 2 × (लम्बाई + चौड़ाई)

प्रश्न 5.
दी हुई आकृति में, (i) ∆ABE (ii) आयत BCDE, का परिमाप ज्ञात कीजिए। किसका परिमाप ज्यादा है?

हल :

(ii) आयत BCDE का परिमाप

चूँकि, 8\(\frac {17}{20}\) > 7\(\frac {5}{6}\), इसलिए, त्रिभुज ABE का परिमाप, आयत BCDE के परिमाप से ज्यादा है।

प्रश्न 6.
सलील एक तस्वीर को किसी फ्रेम (चौखट ) में जड़ना चाहता है। तस्वीर 7\(\frac {3}{5}\) cm चौड़ी है। चौखट में उचित रूप से जड़ने के लिए तस्वीर की चौड़ाई 7\(\frac {3}{10}\) cm से ज्यादा नहीं हो सकती। तस्वीर की कितनी काट-छाँट की जानी चाहिए?
हल :
तस्वीर की चौड़ाई = 7\(\frac {3}{5}\) cm
फ्रेम की चौड़ाई = 7\(\frac {3}{10}\) cm
इसे फ्रेम में फिट करने के लिए काट-छाँट करनी चाहिए।

प्रश्न 7.
रीतू ने एक सेब का \(\frac {3}{5}\) भाग खाया और शेष सेब उसके भाई सोमू ने खाया। सेब का कितना भाग सोमू ने खाया? किसका हिस्सा ज्यादा था? कितना ज्यादा था?
हल :
सोमू ने खाया = 1 – \(\frac{3}{5}=\frac{5}{5}-\frac{3}{5}=\frac{2}{5}\)
चूँकि \(\frac {3}{5}\) > \(\frac {2}{5}\), अतः रीतू का हिस्सा ज्यादा था।
उसने (\(\frac{3}{5}-\frac{2}{5}\)) = \(\frac {1}{5}\) भाग ज्यादा खाया।

प्रश्न 8.
माइकल ने एक तस्वीर में रंग भरने का कार्य \(\frac {7}{12}\) घण्टे में समाप्त किया। वैभव ने उसी तस्वीर में रंग भरने का कार्य \(\frac {3}{4}\) घण्टे में समाप्त किया। किसने ज्यादा समय कार्य किया? यह समय कितना ज्यादा था?
हल :
माइकल ने तस्वीर को रंगा = \(\frac {7}{12}\) घण्टे में वैभव ने उसी तस्वीर को रंगा = \(\frac {3}{4}\) घण्टे
या \(\frac{3 \times 3}{4 \times 3}=\frac{9}{12}\) घण्टे में
चूँकि \(\frac {9}{12}\) > \(\frac {7}{12}\)
अतः वैभव ने अधिक समय कार्य किया
= \(\frac{9}{12}-\frac{7}{12}=\frac{2}{12}\) घण्टे = \(\frac {1}{6}\) घण्टे
अतः वैभव ने \(\frac {1}{6}\) घण्टे अधिक कार्य किया।