Chapter 16 Light

Question 1. Part of the eye which controls the light entering is called

(a) iris

(b) cornea

(c) lens

(d) retina

Question 2. We can see a non-luminous object when light:

(a) emitted by the object falls on the eye.

(b) is reflected from the object towards our eye.

(c) completely passes through the object.

(d) gets completely absorbed by the object.

Question 3. Light is falling on surface S1, S2, S3 as shown in Fig.16.1.

Surfaces on which the angle of incidence is equal to the angle of reflection is/are

(a) S1 only

(b) S1 and S2 only

(c) S2 and S3

(d) all the three surfaces

Question 4. A tiny mirror M is fixed on a piece of cardboard placed on a table. The cardboard is illuminated by light from a bulb. The position of eye with respect to position of bulb is shown in Fig.16.2 as A, B, C and D. In which position mirror will be visible?

a. A

b. B

c. C

d. D

Question 5. A small hole P is made in a piece of cardboard. The hole is illuminated by a torch as shown in Fig. 16.3. The pencil of light coming out of the hole falls on a mirror.

At which point should the eye be placed so that the hole can be seen?

(a) A

(b) B

(c) C

(d) D

Question 6. Two mirrors A and B are placed at right angles to each other as shown in Fig.16.4.

A ray of light incident on mirror A at an angle of $25^\circ$ falls on mirror B after reflection. The angle of reflection for the ray reflected from mirror B would be

(a) $25^\circ$

(b) $50^\circ$

(c) $65^\circ$

(d) $115^\circ$

Question 7. Which of the following statements is correct regarding rods and cones in the human eye?

(a) Cones are sensitive to dim light.

(b) Cones are sensitive to bright light.

(c) Rods are sensitive to bright light.

(d) Rods can sense colour.

Question 8. In the figure of the human eye (Fig.16.5), the cornea is represented by the letter

(a) A

(b) B

(c) C

(d) D

Question 9. Name the part of the eye which gives colour to the eyes.

Question 10. Boojho while waving his hand very fast in front of his eyes, observes that his fingers appear blurred. What could be the reason for it?

Question 11. How many times is a ray of light reflected by two plane mirrors placed parallel and facing each other?

Question 12. The angle between incident ray and reflected ray is $60^\circ$. What is the value of angle of incidence?

Question 13. The distance between the object and its image formed by a plane mirror appears to be $24$ cm. What is the distance between the mirror and the object?

Question 14. What happens to light when it gets dispersed? Give an example.

Question 15. Draw Fig.16.6 showing the position of the plane mirror. Also label the angle of incidence and angle of reflection on it.

Question 16. Look at Fig.16.7. Can the image of the child in it be obtained on a screen?

Question 17. Eyes of the nocturnal birds have large cornea and a large pupil. How does this structure help them?

Question 18. What kind of lens is there in our eyes? Where does it form the image of an object?

Question 19. Which part of the eye gets affected if someone is suffering from cataract? How is it treated?

Question 20. Boojho planned an activity to observe an object A through pipes as shown in Fig. 16.8, so that he could see objects which he could not directly see.

(a) How many mirrors should he use to see the objects?

(b) Indicate the positions of the mirrors in the figure.

(c) What must be the angle with respect to the incident light at which he should place the mirrors?

(d) Indicate the direction of rays in the figure.

(e) If any of the mirrors is removed, will he be able to see the objects?

Question 21. There is a mistake in each of the following ray diagrams given as Fig. 16.9 a, b, and c. Make the necessary correction (s).

Question 22. Explain the process which enables us to perceive motion in a cartoon film.

Question 23. How is the phenomenon of reflection used in making a kaleidoscope? What are the applications of a kaleidoscope?

Question 24. Fig. 16.10 shows the word REST written in two ways in front of a mirror. Show how the word would appear in the mirror.

Question 25. Write down the names of parts of the eye in the blank spaces shown in Fig. 16.10.