Wave Optics Mock Test – Class 12 Physics

1. A graph is plotted with on the vertical axis and on the horizontal axis for monochromatic light. If the slope is , the wavelength is

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

3. A monochromatic wave travels in a medium with speed and frequency . Its wavelength in that medium is

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

5. If two equal-intensity coherent waves have path difference , their resultant intensity is

6. A ray is incident from air on a medium of refractive index . At the polarising angle, the refracted angle satisfies

7. A student draws the electric field vibration of reflected light at Brewster angle along the reflected ray. The drawing is incorrect because

8. Intensity in wave optics is connected more directly with

9. Coherent waves with intensities and can produce a maximum resultant intensity of

10. A graph of intensity versus screen position in a Young's double-slit experiment has the central bright fringe at . The nearest dark fringes should appear at

11. Consider the following statements about Malus' law and polariser chains.
Statement I: Malus' law is applied to plane-polarised light incident on an analyser.
Statement II: Unpolarised light becomes half as intense after one ideal polariser.
Statement III: Two crossed ideal polarisers with no middle polariser transmit maximum intensity.

12. Assertion: A thin transparent sheet placed in front of one slit shifts the entire Young's double-slit fringe pattern.
Reason: The sheet introduces an extra optical path in one beam.

13. A microscope is used first with air and then with an oil-immersion medium of higher refractive index, keeping the objective geometry suitable. The resolution improves mainly because

14. A star's spectral line is observed at a slightly shorter wavelength than its known laboratory wavelength. The observation is best described as

15. At a point, two equal-amplitude coherent waves have phase difference . If increasing by one wavelength changes by , the interference condition there

16. Assertion: The direction of propagation of a wavefront is normal to the wavefront.
Reason: In Huygens' construction, the new wavefront is obtained as the forward envelope of secondary wavelets.

17. A double-slit pattern has equally spaced bright and dark fringes. If the distance from the central bright fringe to the first dark fringe is , the fringe width is

18. A transparent medium has . Another has . For incidence from air, the medium with has

19. A set of parallel plane wavefronts in a uniform medium has equal spacing. This equal spacing physically represents

20. A light wave goes from medium to medium . Its wavelength changes from to . If the angle of incidence is , then is

21. The first dark fringe on one side of the central bright fringe corresponds to

22. A graph description is given below.

The source pair more suitable for sustained interference is

23. Inside a liquid of refractive index , light is incident on the liquid-air surface. Taking air as , the ray is totally internally reflected when

24. 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

25. Use the wavefront description below.

The limiting angle described in the passage is

26. A notebook table lists some wave-optics symbols and units.

The row that must be revised is

27. At normal incidence on a plane boundary, a light wave enters a medium where its speed changes. The direction of the ray does not bend because

28. Consider the following statements about dark fringes in Young's double-slit experiment.
Statement I: The central fringe is dark when the two slits are symmetrically placed.
Statement II: The first dark fringe from the centre corresponds to path difference .
Statement III: Dark fringes occur symmetrically on both sides of the central bright fringe.

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

30. Unpolarised light of intensity passes through three ideal polarisers. The second polariser is at to the first, and the third is at to the second. The final intensity is

31. A graph is plotted for a Young's double-slit experiment with fringe width on the vertical axis and on the horizontal axis, keeping and fixed. The slope of the graph is

32. A wavefront explanation of total internal reflection says that beyond the critical angle

33. The diffraction pattern of a single slit is evidence against a purely geometrical ray description because it shows

34. In Young's double-slit experiment, the approximation becomes unreliable far from the central region mainly because

35. Two light waves reach the same point with equal amplitudes and the same phase. The resultant amplitude at that point is

36. Consider the following statements about fringe width in Young's double-slit experiment.
Statement I: The spacing between consecutive bright fringes is equal to the spacing between consecutive dark fringes.
Statement II: The distance between a bright fringe and its nearest dark fringe is .
Statement III: Increasing while keeping and fixed increases .

37. A table compares possible source pairs for observing sustained interference.

The row that needs correction is

38. Use the reflection arrangement described below.

If the incident part near travels a distance in the same time and in the same medium, the relation between these distances is

39. A record of three wavefronts is shown below.

The row that needs correction is

40. Polarisation of light means that the vibrations of the light wave are

41. Match the observation with the wave-optics idea most closely involved.

42. Two points of a light wave are said to be in the same phase when they

43. Two sources emit light of the same frequency, but their phase difference changes irregularly with time. They should be classified as

44. A -wide single slit is illuminated by light of wavelength . The approximate angular width of the central maximum is

45. Two coherent light waves reach a point with path difference . Their phase difference is

46. For the same two coherent waves with and , the minimum possible resultant intensity is

47. In Young's double-slit experiment with white light, the central fringe is white because

48. A material has a larger polarising angle than another material for incidence from air. The best inference is that the first material has

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

50. For light going from medium to medium , where , the critical angle satisfies