7th Class Science Ch 11 Light: Shadows and Reflections

Class 7 Science
Light and Shadows — Questions & Answers

1. Which of the following are luminous objects?
Mars, Moon, Pole Star, Sun, Venus, Mirror

Answer: Sun and Pole Star are luminous objects because they make their own light. Others are non-luminous objects.

2. 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

Correct Matching:
• Pinhole camera → Forms an inverted image
• Opaque object → Blocks light completely
• Transparent object → Light passes almost completely through it
• Shadow → The dark region formed behind the object

3. 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?

Answer: Only Sahil can see the flame because light travels in straight lines through the straight pipe.

4. Look at the images shown in Fig. 11.17 and select the correct image showing the shadow formation of the boy.

Answer: Image (b) is correct. The shadow forms opposite to light source as a dark shape.

5. 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 shadow formed in both scenarios from the options provided (a and b).

Answer: When ball is closer to torch, shadow is bigger. When ball is closer to wall, shadow is smaller.

6. Based on Fig. 11.18, match the position of the torch in Column A with the characteristics of the shadow in Column B.

Correct Matching:
• 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 → A bright spot would appear on the screen
• If two torches are present in the set-up on the left side of the ball → Two shadows would appear on the screen

7. 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.

Answer: The image will be upside-down and smaller than the real tree. Top becomes bottom and bottom becomes top.

8. 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.

Answer: The image appears sideways reversed, meaning left becomes right and right becomes left. This happens because light reflects from mirror.

9. Measure the length of your shadow at 9 A.M, 12 P.M, and 4 P.M 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?

Answer:
(i) Shadow is shortest at 12 P.M (noon time).
(ii) At noon, sun is directly above us, so light falls straight down making shortest shadow.

10. 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.

Answer: (i) Both statements are true. Plane mirrors make sideways reversed images, and letters T and O look same when reversed.

11. Suppose you are given a tube of the shape shown in Fig. 11.20 and you have a plane mirror 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.

Answer: Yes, this tube can make a periscope. Fix two mirrors at 45-degree angles at both bends of tube.

12. 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.

Answer: When birds fly high, they are far from ground. Sunlight is very bright and spreads out, making shadow very faint.