Class 12th Physics Chapter 9 Ray Optics and Instruments VVI Objective Question

Ray Optics And Optical Instruments

1. Optical fibers communication is based on which of the following phenomena?

(A) Total internal reflection

(B) Scattering

(C) Diffraction

(D) Refraction

2. To get three images of a single object, one should place two plane mirrors at an angle of ……

(A) 60°

(B) 90°

(C) 120°

(D) 30°

3. In which mirror the image of an object always appears diminished and virtual?

(A) Plane

(B) Convex

(C) Concave

(D) None of these

4. With an increase in wavelength the refractive index:

(A) Decreases

(B) Increases

(C) Remains unaffected

(D) None of these

5. An object is placed between two plane mirrors inclined to each other at an angle of 60° The maximum number of images seen will be :

(A) 2

(B) 3

(C) 5

(D) 6

6. For which of the following pairs is the critical angle the smallest :

(A) Water-air

(B) Glass-water

(C) Glass-air

(D) Glass-Glass

7. When light enters glass from air, its wavelength :

(A) Increases

(B) Decreases

(C) Remains unchanged

(D) None of these

8. Two lenses of power -1.5 D and +2.5 D are placed in contact. The focal length of combination will be :

(A) 1 m

(B) 5 m

(C) 10 m

(D) 20 m

9. The length of an astronomical telescope is 16 cm and its magnifying power is 3. The focal length of the lenses will be :

(A) 4 cm, 12 cm

(B) 4 cm, 8 cm

(C) 4 cm,2 cm

(D) 8 cm, 4 cm

10. A spherical mirror is immersed in water, its focal length will

(A) Increase

(B) Decrease

(C) Remain constant

(D) None of these

11. A ray of light goes from glass (refractive index=5/3) to water (4/3). The critical angle will be :

(A) sin-1(1/2)

(B) sin-1(4/5)

(C) sin-1(5/6)

(D) None of these

12. A thin prism (refractive index = 3/2) in air is immersed in a liquid of refractive index 5/4. The ratio of angle of deviations in the two cases will be:

(A) 15/8

(B) 8/15

(C) 5/2

(D) 2/5

13. The refractive index of the material of an equilateral prism is √3. The angle of minimum deviation for the prism is :

(A) 30°

(B) 37°

(C) 45°

(D) 60°

14. Which colour of light has a shortest wavelength ?

(A) red

(B) yellow

(C) blue

(D) violet

15. For which colour of ray the refractive index of glass is largest ?

(A) red

(B) yellow

(C) blue

(d) violet

16. Which colour of light has longest wavelength ?

(A) red

(B) yellow

(C) blue

(D) violet

17. The component of white light that suffers the smallest deviation when passed through a glass prism is

(A) red

(B) violet

(C) green

(D) yellow

18. The power of a convex lens (refractive index 1.50) when immersed in water (refractive index 1.33)

(A) increases

(B) decreases

(C) remains unchanged

(D) None of these

19. As the wavelength is increased, the value of the refractive index of glass

(A) increases

(B) decreases

(C) remains the same

(D) None of these

20. If there are two lenses of powers 2 diopters and 3.5 diopters in contact, the power of the combination will be

(A) +1 D

(B) -1.5 D

(C) 2D

(D) -3.5 D

21. The ray of light does not deviate when it

(A) reflects from a plane mirror normally

(B) reflects from a plane mirror obliquely

(C) passes through a prism

(D) passes through a slab by refracting at parallel interfaces of slabe

22. The unit of power of a lens is

(A) lambda

(B) candela

(C) diopter

(D) watt

23. The power of a convex lens of focal length 10cm will be

(A) -10 D

(B) +10 D

(C) 95D

(D) +5 D

24. Mostly colour-blind eyes cannot distinguish between

(A) red and blue

(B) blue and green

(C) red and green

(D) red and yellow

25. When a red flower’ is viewed through a green glass, it appears

(A) red

(B) green

(C) yellow

(D) black

26. If the distance between an object and its real image formed in a convex lens is 4f, the magnitude of magnification of the image is

(A) less than one

(B) equal to one

(C) more than one

(D) zero

27. A biconvex lens can form virtual image if the object lies

(A) between the lens and its focus

(B) at the focus

(C) between f and 2f

(D) at infinity

28. A parallel beam of rays strikes the plane surface of a thin planoconvex lens giving focal length f. If the lens be inverted, the focal length will be

(A) greater

(B) smaller

(C) of the same value

(D) zero

29. An object lies at 10 cm from a convex mirror of curvature radius 20 cm. The image distance is

(A) 20 cm

(B) 40 cm

(C) 5 cm

(D) infinite

30. When concave lens of glass is immersed in water, it becomes

(A) less convergent

(B) convergent

(C) less divergent

(D) more divergent

31. If the focal length of a lens is 20cm, its power will be

(A) 5 diopter

(B) 20 diopter

(C) 0.5 diopter

(D) 0.05 diopter

32. If the power of a lens is +1D, its focal length will be

(A) 1 meter

(B) 0,5 meter

(C) 2 meter

(D) 1.5 meter

33. When two converging lenses of same focal length fare placed in contact, then the focal length of the combination is

(A) f

(1) 2f

(C) f / 2

(D) 3f

34. A biconvex lens of air bubble in water will behave in the same way as a

(A) converging lens

(B) diverging lens

(C) glass slab

(D) concave mirror

35. Two convex lenses are in contact. The equivalent lens is

(A) convex

(B) concave

(C) planoconcave

(D) cylindrical

36. The optical fibre works on the principle of

(A) Scattering

(B) Refraction

(C) Dispersion

(D) Total internal reflection

37. A convex lens of focal length 40 cm is in contact with a convex lens of focal length 25 cm. The power of the combination is

(A) -1.5 D

(B) -6.5 D

(C) +6.5 D

(D) +5.6 D

38. A coloured image is formed when white rays pass through a thick lens because of

(A) reflection of light

(B) refraction of light

(C) chromatic aberration

(D) spherical aberration

39. The equivalent focal length of the combination of two lenses with powers -15D and +5D is

(A) -10 cm

(B) -20 cm

(C) +10 cm

(D) None of these

40. Which has larger difference in focal length ?

(A) in telescope

(B) compound microscope

(C) in both

(D) None of these

41. The image formed by objective lens of a compound Microscope is :

(A) Virtual and diminished

(B) Real and diminished

(C) Real and large

(D) Virtual and Large

Ans.-(C)

42. A convex lens is dipped in a liquid, whose refractive index is equal to refractive index of material of lens. Then its focal length will :

(A) becomes zero

(B) become infinite

(C) decrease

(D) increase

43. To remove hyper metropia lens used is :

(A) Convex

(B) Concave

(C) Cylindrical

(D) Plano-convex

44. Which of the following phenomena taken place when a monochromatic light is incident on a prism ?

(A) Dispersion

(B) Deviation

(C) Interference

(D) All of the above

45. The resolving power of human eye (in minute) is :

(A) 1 / 60

(B) 1

(C) 10

(D) 1 / 2