ORBIT MBBS PREPARATION

Refraction through prism

1. A ray of light suffers minimum deviation when incident on a 60 prism of refractive index 2 . The

angle of incidence is:

a) sin-1 (0.8) b) 60 c) 45 d) 30

2. A ray is incident at an angle of incidence I on one face of a prism of small angle A and emerges

normally from the opposite surface. If the refractive index of the material of the prism is , the angle

of incidence i is nearly equal to:

a) A/ b) A/2 c) A d) A/2

3. A ray of light passes through an equilateral prism of glass in such a manner that the angle of

incidence is equal to the angle of emergence and each of these angles is equal to (3/4) of the angle of

prism. The angle of deviation is:

a) 45 b) 70 c) 39 d) 30

4. Rainbow is seen due to: a) interference by thin films b) scattering of sunlight c) dispersion of sunlight d) diffraction of sunlight

5. If one face of a prism of prism angle 30 and = 2 is silvered, the incident ray retraces its initial

path. The angle of incidence is:

a) 60 b) 30 c) 45 d) 90

6. Angle of a prism is A and its one surface is silvered. Light rays falling at and angle of incidence of

2A on first surface return back through the same path after suffering reflection at the second silvered

surface. Refractive index of the material is:

a) 2 sin A b) 2 cos A b) (1/2) cos A d) tan A

7. A prism has a refracting angle of 6. When placed in the position of minimum deviation, it produces

a deviation of 3. Then the angle of refraction is:

a) 30 b) 15 c) 45 d) 60

8. A prism has a refracting angle of 6. When placed in the position of minimum deviation, it produces

a deviation of 3. Then the refractive index of the material of the prism is:

a) 3 b) 2 c) 2 d) 1/ 2

9. There is a prism with refractive index equal to 2 and the refracting angle equal to 30. One of the

refracting surfaces of the prism is polished. A beam of monochromatic light will retrace its path if its

angle of incidence over the refracting surface of the prism is:

a) 0 b) 30 45 d) 60

10. A ray falls on a prism ABC (AB=BC) and travels as shown in figure. The minimum refractive index

of the material should be:

a) 4/3 b) 2 c) 1.5 d) 3

11. The angle of deviation for a prism is greatest for:

a) red colour b) violet colour c) blue colour d) green colour

12. When a ray of light is incident normally on one refracting surface of an equilateral prism (Refracting

index of the material of the prism = 1.5): a) emerging ray is deviated by 30 b) emerging ray is deviated by 45 c) emerging ray just grazes the second refracting surface d) the ray undergoes total internal reflection at the second refracting surface

13. If the angle of prism is 60 and angle of minimum deviation is 40, then the angle of refraction will

be:

a) 30 b) 60 c) 100 d) 120

14. In a thin prism of glass (ag =1.5) which of the following relations between the angle of minimum

deviation m and angle of refraction r will be correct?

a) m = r b) m = (1.5)r c) m = 2r d) m = (r/2)

15. The refractive indices of violet and red light are 1.54 and 1.52 respectively. If the angle of prism is

10, the angular dispersion is:

a) 0.02 b) 0.2 c) 3.06 d) 30.6

16. A thin prism P1 with angle 4 and made from glass of refractive index 1.54 is combined with another

thin prism P2 made from glass of refractive index 1.72 to produce dispersion without deviation. The

angle of the prism P2 is:

a) 5.33 b) 4 c) 3 d) 2.6

17. The refracting angle of a prism is A and the refractive index of the prism is cot (A/2). The angle of

minimum deviation is:

a) 180 -3A b) 180 + 2A c) 90 - A d) 180 - 2A

18. If the refractive indices of crown glass for red, yellow and violet colours are respectively r, y and

v, then the dispersive power of this glass would be:

a) 1

y

rv

b)

1

r

yv

c)

ry

yv

d) 1

y

rv

19. Minimum deviation is observed with a prism having angle of prism A, angle of deviation D, angle of

incidence i and angle of emergence e. We then have generally:

a) i > e b) i < e c) i = e d) i = e=D

20. The angle of a prism is 30. The rays incident at an angle of 60 at one refracting face suffer a

deviation of 30. Then the angle of emergence is:

a) 0 b) 30 c) 60 d) 90

21. A parallel beam of white light falls on a convex lens. Images of blue, yellow and red light are formed

on the other side of the lens at a distance of 20 cm, 20.5 cm and 21.4 cm respectively. The dispersive

power of the material of the lens will be:

a) 14/205 b) 9/200 c) 5/214 d) 619/1000

22. The focal length of a converging lens is measured for violet, green and red colours. It is respectively

fv, fg and fr. We will ge:

a) fv = fg b) fv > fr c) fv < fr d) fg > fr

23. Rainbow is formed due to a combination of:

a) dispersion and total internal reflection b) refraction and absorption

c) dispersion and focusing d) refraction and scattering

24. Two thin prisms of crown glass have refracting angles of 10 degrees and 20 degrees. The dispersive

power of these prisms are:

a) 1 : 1 b) 2 : 1 c) 1 : 2 d) 4 : 1

25. Blue colour of sky is due to:

a) scattering of light b) dispersion of light c) interference of light d) sun emits more of light

26. An achromatic combination of lenses is formed by joining: a) 2 convex lenses b) 2 concave lenses c) 1 concave, 1 convex d) convex and plane mirror

27. An achromatic combination of concave and convex lens has power 5 D. If the power of convex lens

is 4 D, then the magnitude of focal of concave lens is:

a) 10 cm b) 200 cm c) 100 cm d) 20 cm

28. A ray of light is incident at 60 on a prism of refracting angle 30. The emerging ray is at an angle

30 with the incident ray. The value of refractive index of the prism is:

a) 4

3 b)

2

3 c) 3 d) 2 3

29. The slitting separation between two colours of the spectrum depends upon:

a) refraction b) reflection c) interference d) diffraction

30. A thin equilateral prism has a refractive index of 1.5. Find the angle of minimum deviation:

a) 30 b) 60 c) 45 d) 90