12th Physics Question

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

Answer:- A

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° 

Answer:- B

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

(A) Plane 

(B) Convex

(C) Concave 

(D) None of these

Answer:- B

4. With an increase in wavelength the refractive index: 

(A) Decreases

(B) Increases

(C) Remains unaffected

(D) None of these

Answer:- A

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 

Answer:- C

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

Answer:- C

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

(A) Increases 

(B) Decreases

(C) Remains unchanged

(D) None of these

Answer:- B

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 

Answer:- A

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 

Answer:- A

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

(A) Increase 

(B) Decrease

(C) Remain constant

(D) None of these

Answer:- C

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

Answer:- B

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 

Answer:- C

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° 

Answer:- D

14. Which colour of light has a shortest wavelength ? 

(A) red

(B) yellow

(C) blue

(D) violet

Answer:- D

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

(A) red

(B) yellow

(C) blue

(d) violet

Answer:- D

16. Which colour of light has longest wavelength ? 

(A) red

(B) yellow

(C) blue

(D) violet

Answer:- A

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

Answer:- A

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

Answer:- B

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

Answer:- B

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

Answer:- B

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 

Answer:- D

22. The unit of power of a lens is 

(A) lambda

(B) candela

(C) diopter

(D) watt

Answer:- C

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

(A) -10 D

(B) +10 D

(C) 95D

(D) +5 D

Answer:- B

24. Mostly colour-blind eyes cannot distinguish between 

(A) red and blue

(B) blue and green 

(C) red and green

(D) red and yellow

Answer:- C

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

(A) red

(B) green

(C) yellow

(D) black

Answer:- D

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 

Answer:- B

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 

Answer:- A

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 

Answer:- C

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

Answer:- C

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

(A) less convergent

(B) convergent 

(C) less divergent

(D) more divergent

Answer:- C

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

Answer:- A

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 

Answer:- A

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

Answer:- C

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

Answer:- B

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

(A) convex 

(B) concave

(C) planoconcave

(D) cylindrical

Answer:- A

36. The optical fibre works on the principle of 

(A) Scattering

(B) Refraction

(C) Dispersion

(D) Total internal reflection 

Answer:- D

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

Answer:- 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

Answer:- C

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

Answer:- A

40. Which has larger difference in focal length ? 

(A) in telescope

(B) compound microscope

(C) in both 

(D) None of these

Answer:- A

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 

Answer:- B

43. To remove hyper metropia lens used is : 

(A) Convex 

(B) Concave

(C) Cylindrical

(D) Plano-convex 

Answer:- A

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 

Answer:- B

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

(A) 1 / 60

(B) 1

(C) 10

(D) 1 / 2

Answer:- D

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