Summary & 50 MCQs with Answers
Wave Optics deals with the phenomena of interference, diffraction, and polarization of light. It explains how light behaves as a wave, the concept of coherent sources, Young's double-slit experiment, diffraction patterns, and applications of polarization.
1. Interference of light occurs when:
A) Two coherent sources overlap ✅
B) Single light ray is reflected
C> Light passes through a prism
D> Only polarized light is used
2. Young’s double-slit experiment demonstrates:
A) Interference of light ✅
B) Diffraction only
C> Polarization only
D> Refraction of light
3. Condition for constructive interference:
A) Path difference = nλ ✅
B) Path difference = λ/2
C> Path difference = λ/4
D> Path difference = n/2 λ
4. Condition for destructive interference:
A) Path difference = (2n+1)λ/2 ✅
B) Path difference = nλ
C> Path difference = λ
D> Path difference = λ/4
5. Coherent sources have:
A) Same frequency and constant phase difference ✅
B) Different frequency
C> Different amplitudes
D> Random phase difference
6. Fringe width in Young’s double-slit experiment is given by:
A) β = λD/d ✅
B) β = d/λD
C> β = λd/D
D> β = D/λd
7. In double-slit experiment, fringe width is independent of:
A) Intensity of light ✅
B) Wavelength
C> Slit separation
D> Distance to screen
8. Diffraction occurs when:
A) Wave passes through a narrow slit ✅
B) Light is absorbed
C> Reflection occurs
D> Refraction occurs
9. Central maximum in single slit diffraction is:
A) Brightest and widest ✅
B) Dim and narrow
C> Dark
D> Equal to secondary maxima
10. Width of central maximum is inversely proportional to:
A) Slit width ✅
B) Wavelength
C> Screen distance
D> Light intensity
11. Polarization of light is possible for:
A) Transverse waves ✅
B) Longitudinal waves
C> Both
D> None
12. Unpolarized light consists of:
A) Vibrations in all planes ✅
B) Single plane vibrations
C> Circular waves
D> No vibration
13. Polarizer is used to:
A) Produce plane polarized light ✅
B) Split light into spectra
C> Increase intensity
D> Reflect light
14. Malus’ law gives:
A) Intensity of polarized light ✅
B) Wavelength of light
C> Refractive index
D> Fringe width
15. Intensity after analyzer is:
A) I = I₀ cos²θ ✅
B) I = I₀ sin²θ
C> I = I₀
D> I = 0
16. Path difference for first minimum in single slit diffraction:
A) λ ✅
B) λ/2
C> 2λ
D> λ/4
17. Diffraction grating separates light into:
A) Spectral components ✅
B) Interference fringes
C> Polarization planes
D> Reflection rays
18. Number of maxima in diffraction depends on:
A) Wavelength and slit separation ✅
B) Light intensity
C> Screen distance only
D> Polarization
19. Secondary maxima are:
A) Less bright than central maximum ✅
B) Brighter than central
C> Same as central
D> Absent
20. Coherent sources maintain:
A) Constant phase difference ✅
B) Variable phase difference
C> Same intensity only
D> Different frequency
21. Optical path difference depends on:
A) Refractive index and distance ✅
B) Intensity only
C> Wavelength only
D> Polarization
22. Number of fringes in double slit is:
A) Width of screen / fringe width ✅
B) Distance between slits
C> Wavelength only
D> Intensity only
23. Diffraction pattern is sharper for:
A) Narrower slit ✅
B) Wider slit
C> Any slit
D> Thick slit only
24. First minimum in diffraction occurs at:
A) sinθ = λ/a ✅
B) sinθ = a/λ
C> sinθ = 2λ/a
D> sinθ = λ/2a
25. Polarization reduces intensity by:
A) 50% for unpolarized light ✅
B) 25%
C> 75%
D> 100%
26. Plane of polarization is defined by:
A) Direction of vibration ✅
B) Wavefront direction
C> Propagation only
D> None
27. Polarization by reflection occurs at:
A) Brewster angle ✅
B) 45° incidence
C> Normal incidence
D> Any angle
28. Brewster angle θB is given by:
A) tanθB = n₂/n₁ ✅
B) sinθB = n₂/n₁
C> cosθB = n₂/n₁
D> tanθB = n₁/n₂
29. Width of central maximum in single slit diffraction is:
A) 2λL/a ✅
B) λL/a
C> λ/a
D> 2a/λ
30. Path difference in two-source interference:
A) Difference in distances from sources ✅
B) Sum of distances
C> Equal to wavelength always
D> Independent of source
31. Interference fringes disappear when:
A) Sources become incoherent ✅
B) Light intensity increases
C> Wavelength decreases
D> Slit width increases
32. Diffraction is prominent when slit width is:
A) Comparable to wavelength ✅
B) Much larger than wavelength
C> Much smaller than wavelength
D> Any size
33. Coherent sources can be produced using:
A) Single source and beam splitter ✅
B) Two independent sources
C> Any light sources
D> Diffraction grating
34. Interference maxima occur at:
A) Δ = nλ ✅
B) Δ = λ/2
C> Δ = λ/4
D> Δ = n/2 λ
35. Interference minima occur at:
A) Δ = (2n+1)λ/2 ✅
B) Δ = nλ
C> Δ = λ/4
D> Δ = λ
36. Intensity at destructive interference:
A) Zero ✅
B) Maximum
C> Half
D> Depends on wavelength
37. Diffraction pattern is symmetric about:
A) Central maximum ✅
B) First minimum
C> Edge of slit
D> Any point
38. Rayleigh criterion applies to:
A) Resolving power ✅
B) Interference only
C> Polarization only
D> Diffraction grating
39. Number of lines per unit length in grating is:
A) Grating element N ✅
B) Slit width
C> Wavelength
D> Intensity
40. Diffraction reduces intensity due to:
A) Spreading of wave ✅
B) Absorption
C> Reflection
D> Polarization
41. Polarizer + analyzer intensity:
A) I = I₀ cos²θ ✅
B) I = I₀ sin²θ
C> I = I₀
D> I = 0
42. Optical path length = n × geometric path ✅
A) Refractive index × distance ✅
B) Wavelength only
C> Path difference
D> None
43. Number of bright fringes on screen:
A) Screen width / fringe width ✅
B) Slit width
C> Wavelength
D> Intensity
44. Diffraction is more for:
A) Narrow slit ✅
B) Wide slit
C> Medium slit
D> Any slit
45. Principal maxima in diffraction grating are:
A) Bright and sharp ✅
B) Dim
C> Absent
D> Broad
46. Secondary maxima in single slit:
A) Less bright than central ✅
B) Brightest
C> Equal to central
D> Absent
47. Resolving power depends on:
A) Aperture size and wavelength ✅
B) Intensity only
C> Slit width only
D> Polarization
48. Light must be coherent to:
A) Form stable interference pattern ✅
B) Show diffraction only
C> Polarize
D> Travel straight
49. Coherent sources can be produced using:
A) Single source + beam splitter ✅
B) Two independent sources
C> Random sources
D> Polarizer only
50. Wave Optics phenomena include:
A) Interference, diffraction, polarization ✅
B) Reflection only
C> Refraction only
D> None