Haryana State Board HBSE 6th Class Science Solutions Chapter 11 Light Shadows and Reflection Textbook Exercise Questions and Answers.
Haryana Board 6th Class Science Solutions Chapter 11 Light Shadows and Reflection
HBSE 6th Class Science Light Shadows and Reflection Textbook Questions and Answers
Rearrange the boxes given below to make a sentence that helps us understand opaque objects.
Classify the objects or materials given below as opaque, transparent or translucent and luminous or non-luminous:
Air, water, a piece of rock, a sheet of aluminium, a mirror, a wooden board, a sheet of polythene, a CD, smoke, a sheet of plane glass, fog, a piece of red hot iron, an umbrella, a lighted fluorescent tube, a wall, a sheet of carbon paper, a flame of a gas burner, a sheet of card board, a lighted torch, a sheet of cellophone, a mix mesh, kerosene stone, sun, firefly, moon.
(i) Opaque things: A piece of rock, a sheet of aluminum, a mirror, a wooden board, a wall, a sheet xrd board.
(ii) Transparent things: Air, water, a sheet of plane glass.
(iii) Translucent things: A sheet of polythene, a CD, smoke, fog, a sheet of carbon paper, a sheet of cellphone.
(iv) Luminous things: A piece of red hot iron, a lighted fluorescent tube, the flame of a gas burner, a lighted torch, sun, fixfly, moon.
(v) Non-luminous things: An umbrella, a wire mesh, kerosene stove.
Can you think of creating a shape that would give a circular shadow if held in one way and a rectangular shadow if held in another way?
Yes, we can think of creating a shape that would give a circular shadow if held in one way and a rectmigular shadow if held in another way. If we held a round card board in front of source of light, it will create a round shadow on the ground and if we turn it at some other position, then it creats a rectangular shadow.
In a completely dark room, if you hold up a mirror in front of you, will you see a right-left inverted image of yourself in the mirror?
In a completely dark room, we cannot see our right-left inverted image in the mirror, because there is no mrce of light and we only can see our image in the mirror, when light is reflected from the mirror.
HBSE 6th Class Science Light Shadows and Reflection Important Questions and Answers
Very Short Answer Type Questions
Does the flame of a gas stove emit light?
Yes, a gas stove flame emits light.
Give one example of a living thing which emits light.
Firefly (Jugnu) is a living source of light.
Give the names of four different sources of light.
Sources of light are: Sun, stars, firefly, electric bulb etc.
How does light travel from one point to the other?
Light travels from one point to other in straight line.
What is the shape of the shadow?
It is similar to the object which forms shadow.
How are shadows formed?
Light coming from the source of light falling on the objects obstructed by the objects and does not go ahead. So a shadow is formed.
Are the edges of shadow sharp and distinct?
Yes, the edges of the shadow are sharp and distinct.
Does the direction of shadow change during the day?
Yes, the direction of shadow changes because the position of the sun changes during the day.
Does, the length of shadow change from season to season?
Yes. The length of shadow changes from season to season.
What is a shadow?
A dark patch formed behind an opaque object when it is placed in the path of light is called a shadow.
What is umbra?
A region of total darkness is called umbra. No ray of light enters this region.
A region of partial darkness which surrounds the umbra is called penumbra, some light rays reach this region.
What do we call a body that shines of its own?
Name one transparent and one opaque body.
Trasparent air, glass, stone, wood (opaque).
What do we call a substance through which light can pass?
Define opaque substance?
The substance through which no light can pass.
Name two translucent substances.
Glazed paper, oil paper.
Name two opaque substances.
Ordinary paper, rubber sheet.
Name two cold sources of light.
Firefly, tube light.
Define reflection of light.
When a beam of light is incident on a smooth surface, apart of it os scattered back into the same medium, it is called reflection.
Short Answer Type Questions
Name any four artificial sources to scattering of fight. The air around the objects of light. allows this scattered fight to pass through it and
2. the oil jaino
Why do objects in a room become transparent, translucent and opaque objects: visible even if sunlight does not enter it?
The objects in a room become visible even if the sunlight dose not enter the room, due to scattering of light. The air around the objects allows this scattered light to pass through it and we can see the objects.
Classify the following into transparent, translucent and opaque objects: Wax, spectacle, a heap of salt, stone, dense smoke, wood, skin, balloon, rubber, membrane of tabla, blood, milk.
Transparent objects: Membrane of tabla, spectacles. Translucent objects: Dense smoke, blood, wax, balloon. Opaque objects: Stone, wood, rubber, milk
How will you convert a transparent glass sheet into a translucent sheet. Suggest any two ways.
(i) By covering one side by butter paper.
(ii) By covering one side by thin sheet of plastics.
State the difference between umbra and penumbra.
|When we switch a torch in a dark room and place a ball in front of the torch, the shadow forms two parts. The central circular path is quite dark and this region is called umbra.||The dark circular path is surrounded by a less dark portion. This shadow part is called penumbra.|
Define regular reflection.
When a beam of light falls on a smooth and polished surface, then regular reflection takes place. The smooth surface gives a clear image due to regular reflection. Example: Reflection from a plane mirror.
State laws of reflection.
Laws of reflection:
(i) The angle of incidents is equal to the angle of reflection.
(ii) The incident ray, reflected ray and the normal are in the same plane.
Name the features of the image formed by a plane mirror.
(i) The image formed by a plane mirror is as far behind the mirror as the object is in front of it.
(ii) It is exactly the same size and shape.
(iii) Image is virtual.
(iv) It is erect but laterally inverted.
Give two effects of light on plants.
(i) Plants use light energy to prepare their own food.
(ii) The tips or short apex of a photogenic plant moves towards it. Light acts as a stimulus to plants.
State two differences between transparent and translucent objects.
|Transparent objects||Translucent objects|
|1. They allow light to pass through them easily.||1. It allows a part of light to pass through it.|
|2. Objects can be seen easily through them.||2. Objects through them can only be seen dimly.|
Distinguish between regular and irregular reflection.
|Regular reflection||Irregular reflection|
|1. It takes place on a smooth and polished surface.||1. It takes place on a rough surface.|
|2. The image is formed after reflection.||2. No image is formed after reflection.|
|3. Light is reflected back in a definite direction into the same medium||3. Light is scattered back into the same medium in all directions.|
What is lateral inversion?
When we look in a plane mirror, we see the image of the objects placed in front of it. The left of the qbject becomes right of the image and the right of the objects becomes left of the image. This is called lateral inversion.
Why is firefly considered to be a cold source of light?
The energy of some chemical reactions within the firefly is released not as heat but as light hence it is called a cold source of light.
Does the length of a shadow change during the day?
Yes, the length of a shadow changes during a day. It is longer in the morning. After that it begins to decrease and it is shortest at 12.00 noon. Then begins to increase in length again.
Under what special circumstances, light does not travel in straight line?
If the size of the object in the path of light is very small (0.0001 cm/less) light bends at the edge of the object. Thus in such case, light does not travel in straight line.
What would be the shape of an object so that it will cast no shadows on the ground in the light of sun?
An object casts no shadow (or very little shadow) on the ground in sunlight when it is either transparent or it is at such a height from the earth that the umbra does not reach the surface of the earth. .
Why is your shadow longest at sunrise and shortest at noon?
In the morning at the time of sunrise and in the evening at the time of sunset light rays falling on the earth are not straight. They are inclined. This is why our shadow at this time both (morning and evening) is the longest. At noon the sun is just over above our head and sun-rays fall vertically on the earth. Due to the vertical sun-rays, our shadow formed at noon is the shortest.
What does an object do when light falls on it?
It may allow to pass the light through or it may completely cut the light from passing through by absorbing the light or it may scatter the light incident on it.
Why is silvered glass used as a mirror?
The silvered glass has a smooth surface and the smoothness helps in forming clear image. Silvering makes it shiny and the shiny surface helps in reducing the absorption.
Long Answer Type Questions
Define the structure and working of a pin-hole camera.
Pin-hole camera: It is a simple application of the rectilinear propagation of light.
It consists of a rectangular card board box, such that its one side is made of ground glass screen, the side opposite to ground glass has a hole in the middle, whose size is equal to the pin-head of a common pin. The box is blackened from inside, so as to absorb any light falling on its walls.
(1) Consider a lighted candle AB, in front of pin-hole camera. The rays starting from points of candles, travel in all directions.
(2) A ray of light starting from point ‘A’ along with AH after passing through the pin-hole falls on ground glass screen at point ‘A’.
Similarly another ray starting from point ‘B’ along with BH after passing through the pin-hole will fall on ground glass screen at point ‘Bj
(3) A1B1 is the image of AB. The image formed here is turned upside down, because light travels in straight line.
Light Shadows and Reflection Class 6 HBSE Notes
- Light is an invisible energy which causes in us a sensation of vision. Though it cannot be seen, it unables us to see things.
- An object which emits light is called a source of light. Sources of light are natural as well as artificial. Sun is the main and brightest source of light. Stars, and jugnu (glow worm) and some fish also emit light.
- Artificial sources of light are man-made sources such as candles, lantern, gas lamps and electric bulbs. Bodies are visible only by ’ the light they send to our eyes. They may be luminous and non-luminous sources.
- Light travels in a straight line, which is called rectilinear propagation of light. It explains the formation of the image of an object in a pin-hole camera.
- When light falls on an object, three things can happen:
→ It is almost completely transmitted through the object.
→ Only one part of it may be transmitted and the rest is absorbed or spread out.
→ It may not be allow’ed to pass through at all. On this basis, we can classify the materials into three categories.
- Transparent materials, which allow light to pass through them and through which we can see clearly are known as transparent materials. Examples: Air, water, glass etc.
- Translucent materials: Substances through which light can pass partially and through which we cannot see clearly are called translucent materials. Examples: Wax paper, butter paper, greased paper etc.
- Opaque materials: Substances which do not allow light to pass through them are called opaque substances. We cannot see through them wood, stone etc.
- In the presence of light, opaque objects act as obstacles to propagate light and form in shadows behind them in the form of umbra and penumbra. The region of space where light from the source does not reach and hence the darkest region is called umbra.
- The region where the light does not reach from all parts of the source is called penumbra.
- When light falls on a smooth surface, they change their direction in a well defined manner, called regular reflection.
- There are two laws of reflection:
→ Angle ofincidence is equal to angle of reflection.
→ Incident ray, reflected ray and the normal all lie in the same plane.
- In a plane mirror, the reflected rays appears to come from some objects kept behind the mirror. This is called a virtual image. A real image can be obtained on a screen.
- Luminous objects. Objects which emit light their own are called luminous objects. Sun, stars, firefly, burning candle, electric bulb and gas lamps are examples of luminous objects. One lumin is the luminous flux of that source whose illuminating power is 1/4rc candela. The brightness is the property measured in units called foot candles. The modern unit now is lux. 1 Foot candle = 10.76 lux.
- Light travels in straight lines:
→ Take three pieces of a card board. Use supports to make them stand vertically on the table.
→ Make holes A, B, C in each of them such that the holes are in one straight line.
→ Now place a candle near hole A at the same height as the hole in the card board.
→ Now see from C. You will notice that the flame of the candle is visible. Now displace one of the card boards from its position so that the holes are no longer in a straight line. The flame is not visible.
This activity shows that light from the candle travels in a straight line from the candle to the eyes.
- Formation of shadows: Shadows are formed when light is obstructed by objects. An opaque object casts a dark shadow, translucent casts a weak shadow and transparent objects cast no shadows.
A shadow of the object is formed in the direction opposite to the side of the source of light. Take a wooden stick about half a metre long. Fix one end of it in open ground where there are no trees and buildings near it. Look its shadow in the morning and mark its points of shadow. Note the direction of sun with respect to the stick. It is formed opposite to the direction of sun.
Again look at the shadow at about 11 a.m. and then about 2 p.m. At 11 a.m. the shadow formed is on the same side and about 2 p.m. shadow is formed in a direction opposite to that seen in the morning.
→ A shadow of an object is formed in the direction opposite to the side of the source of light.
→ Shadow moves according to the movement of sources of light or objects.
→ The length of shadow changes with time.
- Reflection of light: When a beam of light strikes on a plane surface a part of it is turned back into the same direction, it is called reflection.
- On a polished surface, regular reflection takes place and on rough surface irregular reflection takes place.
- Lateral inversion: When we look in a plane mirror, we see the image of the objects placed in front of it. The left of the objects become right and right of the objects become left of the image. Left hand side appears right handside in the image. This is called lateral inversion.