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#### Light Book Back Questions

8th Standard EM

Reg.No. :
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Science

Time : 00:45:00 Hrs
Total Marks : 30
3 x 1 = 3
1. Mirrors having a curved reflecting surface are called as

(a)

plane mirrors

(b)

spherical mirrors

(c)

simple mirrors

(d)

None of the above

2. The centre of a sphere of which the reflecting surface of a spherical mirror is a part is called

(a)

pole

(b)

centre of curvature

(c)

(d)

aperture

3. Focal length is equal to half of the

(a)

centre of curvature

(b)

axis

(c)

(d)

None of the above

4. 2 x 1 = 2
5. Nature of the images formed by a convex mirror is _________.

()

Virtual and erect

6. It the angle of incidence is 45°, then the angle of reflection is ______.

()

45°

7. 5 x 1 = 5
8. Convex mirror

9. (1)

rear - view mirror

10. Regular reflection

11. (2)

plane mirror

12. Snell’s law

13. (3)

Kaleidoscope

14. Refractive index

15. (4)

c / v = μ

16. Multiple reflection

17. (5)

sin i /sin r = μ

3 x 2 = 6
18. The radius of curvature of a spherical mirror is 20 cm. Find its focal length.

19. If two plane mirrors are inclined to each other at an angle of 90°, find the number of images formed.

20. Refractive index of water is 4/3 and the refractive index of glass is 3/2. Find the refractive index of glass with respect to the refractive index of water.

21. 3 x 3 = 9
22. What is called a spherical mirror?

23. Give two applications of a concave and convex mirror.

24. Define the refractive index of a medium.

25. 1 x 5 = 5
26. What is dispersion? Explain in detail.