Light: Shadows and Reflections Class 7 (Curiosity)

Q 1
Question
Which of the following are luminous objects?
Mars, Moon, Pole Star, Sun, Venus, Mirror
Show answer
Hide answer

Q 2
Question
Match the items in Column A with those in Column B.
Column A
Column B
Pinhole camera
Blocks light completely
Opaque object
The dark region formed behind the object
Transparent object
Forms an inverted image
Shadow
Light passes almost completely through it
Show answer
Hide answer

Q 3
Question
Sahil, Rekha, Patrick, and Qasima are trying to observe the candle flame through the pipe as shown in Fig. 11.16. Who can see the flame?
Show answer
Hide answer

Q 4
Question
Look at the images shown in Fig. 11.17 and select the correct image showing the shadow formation of the boy.
Show answer
Hide answer

Q 5
Question
The shadow of a ball is formed on a wall by placing the ball in front of a fixed torch as shown in Fig. 11.18. In scenario (i) the ball is closer to the torch, while in scenario (ii) the ball is closer to the wall. Choose the most accurate representation of the shadows formed in both scenarios from the options provided (a and b).
Show answer
Hide answer

Q 6
Question
Based on Fig. 11.18, match the position of the torch in Column A with the characteristics of the ball's shadow in Column B.
Column A
Column B
If the torch is close to the ball
The shadow would be smaller
If the torch is far away
The shadow would be larger
If the ball is removed from the set-up
Two shadows would appear on the screen
If two torches are present in the set-up on the left side of the ball
A bright spot would appear on the screen
Show answer
Hide answer

Q 7
Question
Suppose you view the tree shown in Fig. 11.19 through a pinhole camera. Sketch the outline of the image of the tree formed in the pinhole camera.
Show answer
Hide answer

Q 8
Question
Write your name on a piece of paper and hold it in front of a plane mirror such that the paper is parallel to the mirror. Sketch the image. What difference do you notice? Explain the reason for the difference.
Show answer
Hide answer

Q 9
Question
Measure the length of your shadow at 9 AM, 12 PM, and 4 PM with the help of your friend. Write down your observations:
(i) At which of the given times is your shadow the shortest?
(ii) Why do you think this happens?
Show answer
Hide answer

Q 10
Question
On the basis of following statements, choose the correct option.
Statement A: Image formed by a plane mirror is laterally inverted.
Statement B: Images of alphabets T and O appear identical to themselves in a plane mirror.
(i) Both statements are true
(ii) Both statements are false
(iii) Statement A is true, but statement B is false
(iv) Statement A is false, but statement B is true
Show answer
Hide answer

Q 11
Question
Suppose you are given a tube of the shape shown in the Fig. 11.20 and two plane mirrors smaller than the diameter of the tube. Can this tube be used to make a periscope? If yes, mark where you will fix the plane mirrors.
Show answer
Hide answer

Q 12
Question
We do not see the shadow on the ground of a bird flying high in the sky. However, the shadow is seen on the ground when the bird swoops near the ground. Think and explain why it is so.
Show answer
Hide answer

Project 1
Project
Have you ever seen a firefly where you live? If no, ask your elders if fireflies were seen earlier in your region. If yes, find out the reasons for their not being seen anymore. Develop a story about it.
Show sample answer
Hide answer
Key Points
Fireflies are vanishing in many places, and a story can spread awareness.
Key Points
Ask elders if fireflies were common earlier in your area.
Find out if you can still see them at night.
Common reasons for their loss are light pollution and lost forests.
Too much building and tourism also harm them.
Write a story that helps people care about fireflies.
A simple story can help protect fireflies and their dark habitats.

Project 2
Project
Repeat Activity 11.4, but this time cover the face of the torch with a coloured transparent paper and observe the colour of the shadow. Repeat this using transparent paper of different colours. Report your conclusions. Also, find out what happens when two or more mirrors are kept at an angle or parallel to each other, and whether a small mirror can form an image of a large object.
Show sample answer
Hide answer
Key Points
Coloured light changes the lit area, and more mirrors make more images.
Key Points
Cover the torch with coloured transparent paper and watch the shadow.
The shadow itself stays dark, but the lit area takes the colour.
Try different coloured papers and note what you see.
Two mirrors at an angle form many images of one object.
A small mirror can still show parts of a large object.
Colour changes the lit area, and angled mirrors multiply the images.

Project 3
Project
You are given a small piece of a plane mirror. Can this piece form an image of an object much larger than the mirror, like a large tree? Think and predict. Then carry out the activity.
Show sample answer
Hide answer
Key Points
Yes, a small mirror can form an image of a much larger object.
Key Points
Take a small piece of plane mirror.
Hold it to reflect a large object like a tree.
Move it until you see the full tree in it.
The whole image fits even in the small mirror.
So mirror size does not limit the image size.
Even a tiny mirror can show the image of a very large object.
☀️ Fascinating Facts
Light from the Sun takes about 8 minutes and 20 seconds to reach Earth.
So we always see the Sun as it was minutes ago.
If the Sun suddenly stopped shining, we would not know at once.
We would find out only after 8 minutes and 20 seconds.