Wave Optics Mock Test – Class 12 Physics

1. Two light waves of the same frequency travel in the same medium. Their amplitudes are in the ratio . If intensity is proportional to the square of amplitude, the ratio of their intensities is

2. A glass plate has polarising angle such that . At this angle, the refracted angle satisfies

3. A polariser is an optical device that

4. If two coherent waves have equal individual intensity , their maximum intensity is

5. A microscope uses light of wavelength and numerical aperture . If the limiting resolution is taken as , the smallest resolvable distance is

6. Unpolarised light of intensity passes through three ideal polarisers. The angle between each neighbouring pair of axes is . The final transmitted intensity is

7. Two coherent beams have amplitudes and . Another pair has amplitudes and . Assuming the same phase stability, the first pair gives better dark-bright contrast mainly because

8. A point in Young's double-slit experiment has path difference . For equal slit intensities, is

9. A reflected ray is observed to make with the plane mirror surface. The angle of incidence is

10. A point in a double-slit experiment receives two waves of equal intensity . The path difference is first and then is increased by . The change in resultant intensity is

11. The fringe width in Young's double-slit experiment is the distance between

12. For a double-slit experiment with , , and , the distance of the first dark fringe from the central bright fringe is

13. Assertion: Two coherent sources can produce a stable interference pattern.
Reason: Coherent sources maintain a constant phase difference.

14. Huygens' construction for refraction at a plane surface leads to the relation

15. Assertion: A very small aperture can make the shadow boundary less sharp.
Reason: When aperture size is comparable to wavelength, diffraction spreading becomes appreciable.

16. A student draws only straight rays through a slit and predicts a perfectly sharp light patch on the screen. This prediction is most likely to be poor when

17. Two independent ordinary bulbs do not usually produce a stable interference pattern on a screen because

18. When unpolarised light is incident on a transparent surface at the polarising angle, the reflected light is

19. The angular width of the central maximum in single-slit diffraction is doubled when

20. For intensities and , two coherent waves have minimum possible resultant intensity

21. A data sheet gives the following pairs for a monochromatic light wave in one medium.

The row that does not fit the usual meaning of the quantity is

22. A claim says, “If two polarisers are crossed, inserting another polariser between them can never increase transmission.” The best evaluation is that the claim is

23. If the slit separation is doubled while and remain fixed, the fringe width

24. Unpolarised light is best represented as light whose electric field vibrations

25. For a plane wavefront crossing from medium into medium , with refractive indices and , the wave-speed relation used in refraction is

26. At Brewster angle for air-to-glass incidence, the reflected light is plane-polarised with vibrations

27. Which observation most directly points to the need for superposition of light waves?

28. A graph description is given below.

The graph should show that

29. Total internal reflection can occur only when light tries to travel

30. Consider the following statements about glare reduction by polaroids.
Statement I: Glare from horizontal surfaces is often partially polarised.
Statement II: A suitably oriented polaroid can reduce a preferred vibration component of reflected glare.
Statement III: A polaroid reduces glare by changing the frequency of reflected light.

31. For a Brewster-angle setup with , the polarising angle is closest to

32. Colours seen in a thin soap film are mainly produced because light waves reflected from the upper and lower surfaces of the film

33. In a Young's double-slit experiment, light of wavelength is used. A transparent sheet of refractive index and thickness is introduced in front of one slit. The fringe pattern shifts by

34. Inside glass, a ray approaches a glass-air boundary. As the angle of incidence in glass is gradually increased, the angle of refraction in air

35. Brewster's law relates the polarising angle and refractive index of the reflecting medium by

36. A table lists symbols used in Young's double-slit experiment.

The row that should be corrected is

37. If the wavelength used in a Young's double-slit experiment is doubled while and remain unchanged, the position of the th bright fringe from the centre

38. A record of overlapping waves is shown below.

The row that needs correction is

39. A claim says, “Making a slit narrower should make the light patch narrower because the opening is smaller.” The wave-optics correction is that

40. A graph of diffraction intensity versus angle for a single slit has a broad central peak and weaker side peaks. The broad central peak represents

41. A construction based on Huygens' principle uses several points on an old wavefront. The physically meaningful new wavefront is not obtained by joining the centres of the secondary wavelets because

42. A wave from source travels farther than a wave from source to reach point . Taking , the phase difference at is

43. In Young's double-slit experiment, the fringe width is given by

44. In Young-type interference, the two narrow slits are usually illuminated by the same source before acting as secondary sources. The main reason is to

45. A statement says, “When two equal beams interfere constructively, energy is created because the maximum intensity becomes instead of .” The correct interpretation is that

46. Light is incident from air into glass. If , , and , the value of is

47. The electric-field direction of a beam is observed at one point. In case P, the direction changes randomly among many transverse directions. In case Q, it remains along one fixed transverse direction. The better classification is

48. Two spherical wavefronts from the same point source are observed at times and , where . If the wave speed is , the increase in radius is

49. A double-slit experiment uses and . For light of wavelength , the screen coordinate where the path difference first becomes is

50. The phase condition for destructive interference is best written as