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Question Bank No: 1

1. A ray of light passes through an equilateral prism such that angle of incidence is equal to the angle of emergence and the latter is equal to $\frac{3}{4}$ the angle of prism .The angle of deviation is

a)		$45^{0}$
b)		$39^{0}$
c)		$20^{0}$
d)		$30^{0}$

2. A ray of light strikes a silvered surface inclined to another one at an angle of $90^{0}$ . Then the reflected ray will turn through
rayoptics-Q20

a)		$0^{0}$
b)		$45^{0}$
c)		$90^{0}$
d)		$180^{0}$

3. Which one of the following spherical lenses does not exhibit dispersion? The radii of curvature of surfaces of lenses are given in diagrams

a)
b)
c)
d)

4. Why sun has elliptical shape when it rises and sets it is due to

a)		refraction
b)		reflection
c)		scaltering
d)		dispersion

5. Which of the prism is used to see infrared spectrum of light?

a)		Rock salt
b)		Nicol
c)		Flint
d)		Crown

6. With respect to air, critical angle in a medium for light of red colour $[λ_{1}] is ϕ$ Other facts remaining same, critical angle for light of yellow colour $[λ_{2}]$ will be

a)		$ϕ$
b)		more than $ϕ$
c)		less than $ϕ$
d)		$\frac{ϕ λ_{1}}{λ_{2}}$

7. A mark at the bottom of a beaker containing liquid appeares to rise by 0.1 m. The depth of the liquid is 1m. The refractive index of liquid is

a)		1.33
b)		9/10
c)		10/9
d)		1.5

8. The minimum magnifying power of a telescope is M.If the focal length of the eye lens is halved.The magnifying power will be come

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

9. If water drop is kept between two glass plates, then its shape is

a)
b)
c)
d)		none of these

10. Which of the following spectrum have all the frequencies from high to low frequency range?

a)		Bend Spectrum
b)		Continous Spectrum
c)		Line Spectrum
d)		Dis continous Spectrum

11. A lens is placed between a source of light and a wall it forms image of area $A_{1}$ and $A_{2}$ on the wall, for its two different positions. The area of the source obtained is

a)		( $A_{1} + A_{2}) / 2$
b)		${[\frac{1}{A_{1}} + \frac{1}{A_{2}}]}^{- 1}$
c)		$\sqrt{A_{1} A_{2}}$
d)		${[(\sqrt{A_{1}} + \sqrt{A_{2}}) / 2]}^{2}$

12. Loss of the ability of eye to focus on near and far objects with advancing age is called

a)		presbyopia
b)		Astigmatism
c)		Hypermetropia
d)		Myopia

13. A movie projector projects an image of length 3.5 m of a 35mm movie filim on a screen. Neglecting absorption of light by the filim and the air, the ratio of the illumination on the screen decreases in the ratio

a)		100:1
b)		$10^{4} : 1$
c)		1:100
d)		1: $10^{4}$

14. An observer looks at a tree of height 15 cm with a telescope of magnifying power 10. To him, the tree appears

a)		10 times taller
b)		15 times taller
c)		10 times nearer
d)		15 times nearer

15. Ducto spherical aberration the image is

a)		blurred
b)		coloured
c)		both a and b
d)		neither a and b

16. Two lenses of focal lengths +10 cm and -15 cm when put in contact behave like convex lens. They will have zero longitudinal chromatic aberration if ratio of dissipative power is

a)		+ 3/2
b)		+2/3
c)		- 3/2
d)		- 2/3

17. Up to what height should water be filled into vessel of height 21 cm .Such that it appears half filled when viewed from above ( $μ_{ω} = 4 / 3)$

a)		8 cm
b)		10. 5 cm
c)		12 cm
d)		14 cm

18. A triangular prism of glass show below. A ray incident normally on one face is totally reflected .If $θ$ is $45^{0},$ The refractive index of glass is
rayoptics-Q4

a)		less than $\sqrt{2}$
b)		equal to $\sqrt{2}$
c)		greater than $\sqrt{2}$
d)		none of the above

19. Time taken by the sun light to pass through a window of thickness 4mm whose refractive index is 1.5 is

a)		2 $\times 10^{- 8} S$
b)		2 $\times 10^{8} S$
c)		2 $\times 10^{- 11} S$
d)		2 $\times 10^{- 11} S$

20. The number of images observable between two parallel plane mirror is

a)		2
b)		4
c)		11
d)		infinite

21. The first laboratory determination of the speed of light was made by

a)		Fizeau
b)		Fou cault
c)		Roemer
d)		Michelson

22. A convex mirror and a concave mirror each of focal length 5 cm, are placed at a distance 15 cm apart facing each other. A point object is placed midway between them. If reflection first takes place at the concave mirror and then at the convex mirror, final image is formed at

a)		15 cm behind the convex mirror
b)		10 cm from the concave mirror and between the 2 mirror
c)		at the pole of concave mirror
d)		at the pole of convex mirror

23. A ray of light is incident at an angle of $60^{0}$ on one face of a prism which has an angle of $30^{0}$ . The ray emerging out of the prism makes an $30^{0}$ with the incident ray.Refractive index of material of prism is

a)		1.73
b)		1.5
c)		1.2
d)		1.6

24. A ray of light is incident at an angle of $60^{0}$ on one face of a prism which has an angle of $30^{0}$ . The ray emerging out of the prism makes an $30^{0}$ with the incident ray. The angle of emergence is

a)		$60^{0}$
b)		$30^{0}$
c)		$90^{0}$
d)		$0^{0}$

25. The speed of light in air is 3 $\times 10^{8} {ms}^{- 1}$ What will be its speed in diamond whose refractive index is 2.4?

a)		3 $\times 10^{8} {ms}^{- 1}$
b)		1.25 $\times 10^{8} {ms}^{- 1}$
c)		332 ${ms}^{- 1}$
d)		7.2 $\times 10^{8} {ms}^{- 1}$

26. With fixed positions of the object and the image pins in the displacement method, the second position of the lens can be obtained only when the diatance D between the object pin and image pin is

a)		less than 4f
b)		equal to 4f
c)		more than 4f
d)		3f or 4f

27. Light of a certain colour has 2000 waves to the millimeter in air. What will be the wavelength of this light in a medium of refractive index 1.25?

a)		1000A
b)		2000A
c)		3000A
d)		4000A

28. A thin lens has focal length f and its aperture has diameter d. It forms an image of intensity I. Now the central part of the aperture upto diameter d/2 is blocked by an opaque paper. The focal length and the image intensity will change to

a)		f/2 and 1/2
b)		f and 1/4
c)		3f/4 and 1/2
d)		f and 3/4

29. A luminous object is kept at a fixed distance from a screen and with the help of a convex lens an image is obtained on the screen. The lens is then moved till another image is obtained on the screen. If the sizes of the images be 2cm and 8cm and the distance between the object and the screen be 90cm, then size of the object is

a)		2 cm
b)		8 cm
c)		4 cm
d)		6 cm

30. In optical fibre the following principle is used

a)		total internal reflection
b)		scattering
c)		successive reflection
d)		refraction

31. A plano-convex lens of focal length 60cm is silvered on its plane face. An object is placed at a distance of 60 cms from it. The distance of the image from it, is

a)		50 cm
b)		55 cm
c)		v
d)		300/7 cm

32. Total internal reflection can occur when light passes from

a)		a rarer medium to a denser medium
b)		one medium to another of equal refractive index
c)		a denser to a rarer medium
d)		one medium to another of equal absorption coefficient

33. The refractive index of water and glass with respect to air are 1.3 and 1.5 respectively. what will be the refractive index of glass with respect to water?

a)		15 $/$ 13
b)		13 $/$ 15
c)		2
d)		3

34. An equi-convex lens is cut into two halves by a plane AB as shown in Fig. The focal length of each half so obtained is
rayoptics-q15

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

35. To get three images of a single object, one should have two plane mirrors at an angle of

a)		$50^{0}$
b)		$60^{0}$
c)		$30^{0}$
d)		$90^{0}$

36. A parallel beam of light in air is incident on a glass sphere of refractive index 1.5 and diameter 20cm parallel to its horizontal diameter. The rays converge to a point at the distance of d from the centre of the sphere, then d is

a)		20cm
b)		15cm
c)		10cm
d)		5cm

37. Time taken by the sunlight to pass through a window of thickness 4mm whose refractive index is 1.5 is

a)		2 $\times 10^{11} \sec$
b)		2 $\times 10^{8} \sec$
c)		2 $\times 10^{- 11} \sec$
d)		2 $\times 10^{- 8} \sec$

38. A lens behaves as a converging lens in air and a diverging lens in water. The refractive index of the material is

a)		equal to unity
b)		equal to 1.33
c)		between unity and 1.33
d)		greater than 1.33

39. A convex lens of glass is immersed in water compared to its power in air, its power in water will

a)		diminish
b)		increase
c)		remain the same
d)		diminish for red light and increase for blue light

40. A light beam passes from air into a liquid and is deviated by $15^{0}$ when the angle of incidence is $60^{0}$ . What is the index of refraction of the liquid?

a)		$\frac{2}{\sqrt{3}}$
b)		$\frac{\sqrt{3}}{2}$
c)		$\frac{\sqrt{2}}{3}$
d)		$\sqrt{\frac{3}{2}}$

41. The sun (diameter=D) subtends an angle $θ$ radians at the pole of a concave mirror of local length f. The diameter of the images of the sun formed by the mirror is

a)		f $θ$
b)		2f $θ$
c)		$f^{2} θ / D$
d)		D $θ$

42. A 1.7m tall person stands 1.6m in front of a vertical plane mirror. The height of his image will be

a)		1.6m
b)		1.7m
c)		0.85m
d)		3.4m

43. Critical angle for total internal reflection will be smallest for light travelling from

a)		water to glass
b)		glass to air
c)		glass to water
d)		water to air

44. A double convex lens of refractive index $μ_{1} is$ immersed in a liquid of refractive index $μ_{2}$ .This lens will act as

a)		diverging lens if $μ_{1} > μ_{2}$
b)		diverging lens if $μ_{1} < μ_{2}$
c)		converging lens if $μ_{1} = μ_{2}$
d)		converging lens if $μ_{1} < μ_{2}$

45. Radius of curvature of concave mirror is 40cm and the size of image is twice as that of the object. The object distance is

a)		20 cm
b)		30cm
c)		60cm
d)		40cm

46. A converging lens has a focal length in air =20cm. When it is immersed in liquid of refractive index less than the refractive index of the material of the lens, the focal length of lens in the liquid

a)		=20cm
b)		$> 20 cm$
c)		$< 20 cm$
d)		changes the sign

47. The image of an object formed by a device is always virtual and small. The device may be

a)		a glass plate
b)		concave lens
c)		convex lens
d)		concave mirror

48. Two thin lenses, when in contact produce a combination of power + 10D. when they are 0.25 m apart, they produce power of +6 dioptic. Focal length of the two lenses are

a)		12.5 cm and 50 cm
b)		25 cm and 110 cm
c)		25 cm and 50 cm
d)		12.5 cm and 72.5 cm

49. A point source of light is placed 4 m below the surface of water of refractive index 5/3. The minimum diameter of the disc, which shoulf be placed over the source, on the surface of water to cut off all light coming out of water, is

a)		infinite
b)		6 m
c)		4 m
d)		3 m

50. The curved face of a plano-convex lens is silvered. If $μ$ is the refractive index and R the radius of curvature of its curved surface, then the system behaves like a concave mirror of radius

a)		R ( $μ - 1)$
b)		R $μ$
c)		R/ ( $μ - 1)$
d)		R/ $μ$