Here in this post we provided NCERT Exemplar Problem Class 6 Science Light Chapter 11 Full Explanation by group of Science Experts. We have provided here each questions answer with reason behind the answer.
Hope it help you!
Light Class 6 Exemplar full Explanation:
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Multiple Choice Questions
1) Observe the picture given in fig. 11.1 carefully.
A patch of light is obtained at B, when the torch is lighted as shown. Which of the following is kept at position A to get this patch of light?
a) A wooden board
b) A glass sheet
c) A mirror
d) A sheet of white paper
Answer:- c) A mirror
When the mirror is kept at the position A then the patch of light will be obtained.
2) A student observes a tree given in fig. 11.2 through a pin hole camera. Which of the diagrams given in fig. 11.3 (a) to (d) , depicts the image seen by her correctly?
Answer:-b)
3) Four students A,B ,C and D looked through pipes of different shapes to see a candle flame as shown in fig. 11.4.
Who will be able to see the candle flame clearly?
a) A
b) B
c) C
d) D
Answer:- d) D
4) Which of the following is/are not always necessary to observe a shadow?
a) Sun
b) Screen
c) Source of light
d) Opaque object
Answer:- a) Sun
Sun is not always necessary for observing shadow. But screen, source of light, and opaque object is necessary.
5) Paheli observed the shadow of a tree 8:00 a.m., 12:00 noon and 3:00 p.m. which of the following statements is closest to get observation about the shape and size of the shadow?
a) The shape of the shadow of the tree changes but the size remains the same.
b) The size of the shadow of the tree changes but the shape remains the same
c) Both the size and shape of the shadow of the tree change.
d) Neither the shape nor the size of the shadow changes .
Answer:- c) both the size and shape of the shadow of the tree change.
As per the sun changes its position the shadow of the tree also changes in the shape and size both.
6) Which of the following can never form a circular shadow?
a) A ball
b) A flat disc
c) A shoe box
d) An ice cream cone
Answer:-c) A shoe box
Shoe boxes are normally rectangular in shape. Thus a shoe box can never form a circular shadow.
7) Two students while sitting across a table looked down on to its top surface. They noticed that they could see their own and each other’s image. The table top is likely to be made of :
a) Unpolished wood
b) Red stone
c) Glass sheet
d) Wood top covered with cloth
Answer:- c) Glass sheet
If the top surface is made up of glass sheet then then they can see the image of their own and each others
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Very Short Answer Questions
8) You have 3 opaque strips with very small holes of different shapes as shown in fig. 11.5 . If you obtain an image of the sun on a wall through these holes, will the image formed by these holes be the same or different?
Answer:- All the three image formed from holes of the opaque strips will be the same. Image of sun will be same.
9) Observe the picture given in fig. 11.6 A sheet of some material is placed at position ‘p’ , still the patch of light is obtained on the screen. What is the type of material of this type of material of this sheet?
Answer:-
A sheet of Transparent material must be placed at ‘p’.
As given, the patch of light obtained on the screen is same as before. Transparent sheet will allow the light to pass and clear image will obtain. Thus there should be Transparent sheet only.
10) Three torches A, B, and C shown in fig. 11.7 are switched on one by one. The light from which of the torches will not form a shadow of the ball on the screen.
Answer:- Light of torch C will not form any shadow.
Because, for obtaining shadow of object we need an screen opposite to it. Torch A and B are placed on the opposite side of the screen thus when these A and B Torch will start the shadow of football will be obtained on the screen but Torch C is on the side of screen therefore on starting torch C shadow will not obtain.
11) Look at the figure given in fig. 11.8.
Will there be any difference in the shadow formed on the screen in A and B.
Answer:- No. There will not be any difference in the shadow formed on the screen. Because both the metal bowl has same shape and size. Thus the shadow obtained on the screen will be same of both A and B.
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Short Answer Questions
12) Correct the following statements.
I) The colour of the shadow of an object depends on its colour of the object.
Answer:- the colour of the shadow of an object does not depend on the colour of the object.
Shadow is always dark and colour of object does not affect the shadow.
II) Transparent objects allow light to pass through them partially.
Answer:- transparent objects allow most of the light to pass through themnot partially. But Translucent objects allow light to pass through the object partially.
13) Suggest a situation where we obtain more than one shadow of an object at a time.
Answer:- We can obtain more than one shadow of an object of light from more than one source falls on it.
14) On a sunny day, does a bird or an aeroplane flying in the sky cast it’s shadow on the ground? Under what circumstances can we see their shadow on the ground?
Answer:- No. Shadow of flying birds and aeroplanes cannot be seen if it is on high. But if the birds are flying close to the ground or if the aeroplane taking off from the ground then we can see the shadow of it.
15) You are given a transparent glass sheet. Suggest any two ways to make it translucent without breaking it.
Answer:-
A) If the transparent glass is coated with the grease, oil or butter . When we put that on the glass then the transparent glass becomes translucent.
B) If we paste butter paper on the transparent glass then the transparent glass will become translucent.
C) If the glass is rubbed with hard material then the transparent glass will become translucent and the object will not seen clearly through it.
16) A torch is placed at two different positions A and B, one by one, as shown in fig. 11.9.
The shape of the shadow obtained in two positions is shown in fig. 11.10 .
Match the position of the torch and shape of the shadow of the ball.
Answer:-
A → a
a shadow will be obtained when the Torch is placed at position A. As the Torch is placed directly opposite to the screen the shadow of the football will obtain bigger.
B → b
b shadow will obtained when the torch is placed at position B. As the shadow is compressed from sides because the torch is slightly side of the screen and not directly on the opposite direction.
17) A student covered a torch with red cellophane sheet to obtain red light. Using the red light she obtains a shadow of an opaque object. She repeats thus activity with green and blue light. Will the colour of the light affect the shadow? Explain.
Answer:- Shadow is not affected by the colour of the light. Shadow is always a dark coloured patch formed of an object, when an light is covered by an object and a screen is available behind it. Any colour of light or colour of object does not affect an shadow. It is always dark.
18) Is air around us always transparent ? Discuss.
Answer:- Air is present all over surrounding us. air is transparent thus we can see through it. But if there is thick smog , smoke or thick clouds are present then it is difficult to see around . Therefore air is not always transparent.
19) Three identical towels of red, blue and green colour are hanging on a clothes line in the sun. What would be the colour of shadows of these towels?
Answer:- the colour of shadows of all three towels will be the same. Shadow is not affected by the colour of any light or any object. when an object is covered the light a dark coloured patch is fallen on the screen is the shadow therefore shadow does not contain any colour.
20) Using a pinhole camera a student observes the image of two of his friends, standing in sunlight wearing yellow and red shirt respectively. What will be the colours of the shirts in the image?
Answer:- The shirts in the image will be the same as they wear. Image is not affected by the colours of object. Image is exactly same as the object. In size, shape, colour and complete appearance. Therefore when they were in sunlight though the image will be same as the objects are.
21) In fig. 11.11, a flower made of thick coloured paper has been posted on the transparent glass sheet. What will be the shape and colour of shadow seen on the screen?
Answer:-
Shadow don’t have an colour. it is only a dark patch of an object, when an object is placed between light and a screen.
The shadow of the flower made of thick coloured paper will formed on the screen as dark and as same as shape of flower with the stalk.
But colour will not be there in the shadow.
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Long Answer Questions
22) A football match is being played at night in a stadium with flood lights ON. You can see the shadow of a football kept at the ground but cannot see it’s shadow when it is kicked high in the air. Explain.
Answer:-
We can see the shadow of an object when there is screen at a certain distance from the object. If the screen and object are placed at larger distance then we don’t get an shadow. Here the same thing happens, when the football is on the ground we see the shadow but when it is kicked in the air we don’t find the shadow of it.
23) A student had a ball, a screen and a torch in working condition. He tried to form a shadow of the ball on the screen by placing them at different positions. Sometimes the shadow was not obtained. Explain.
Answer:- 1) The Torch may be kept at longer distance from the ball.
2) the ball may be at Longer Distance from the scree.
3) the torch may not be kept on opposite side of an screen so that the shadow could not form on screen.
24) A sheet of plywood , a piece of muslin cloth and that of a Transparent glass, all of the same size and shape were placed at A one by one in the arrangement shown in fig. 11.12 will the shadow be formed in each case. If yes, how will the shadow on the screen be different in each case ? Give reasons for your answer.
Answer:-
No. Shadow will not form in all the cases. Only muslin cloth and plywood will obtain an shadow.
Transparent glass will allow the light to pass from the it and no shadow will obtained on the screen .
Muslin cloth which is a translucent material, if light is passed from that, the shadow will be lighter.
The sheet of plywood is an opaque object. It will completely block the light and shadow will be form is darker in colour.