# MCQs On Interference And Diffraction Of Light

## Difference between Interference and Diffraction

Interference and Diffraction for class 12th Physics generally has a question related to the difference between the two. Following table lists the differences.

Interference Diffraction
It is result of superposition of light from two coherent sources. It is result of superposition of light from different parts of same wavefront.
All bright bands have equal intensity. Intensity of central maxima is highest. Secondary maxima have decreasing intensities.
Dark fringes are almost perfectly dark. Dark fringes are NOT perfectly dark.
Good contrast between bright and dark fringes Poor contrast
For monochromatic light, fringes are of equal widths Never equal widths
Bands are large in number Few in number
Resolving power of instrument is not related to Interference. Resolving power of instrument is related to Diffraction.

These difference between interference and diffraction is very important because many MCQ multiple choice question would be based on them. These interference physics questions are specially significant for class 12th students appearing for competitive exams.

```ZoomPhysics - A Physics learning software (Windows) for students preparing for Engineering & Medical Entrance Exams FREE Download {132 MB}```

## Multiple Choice Questions: Interference And Diffraction Of Light

01. There are three conditions for resolution:
1. Unresolved
2. ______________
3. Completely Resolved

02. Rayleigh’s Criterion for resolution: The images of two objects close to each other are said to be resolved (separate), if the _________ of one falls on the first minima of the other.

03. Insertion of transparent sheet in path of one of the two interfering beams: Fringe shift is __________ (n) {order of fringe}
(a) dependent on
(b) dependent on reciprocal of
(c) dependent on square root of
(d) independent of

05. Name the following: A theoretical criterion to decide whether the optical instrument has resolved the object or not.04. When the Central maxima of one object & first minima of other object Coincides, then the objects are said to be ______ resolved.

06. When the separation of two central maximums is greater than the separation of central maximum and first minimum of any of the two objects, then the objects are said to be _______ resolved

07. True or False: When two central maximas, are Overlapping (shows one peak), then Central maxima of one object & first minima of other object are within each other.

08. When two light waves have same wavelength, they are called _____ sources of light

09. The modification in the intensity of light (redistribution of light energy) produced by the superposition of two or more light waves is called ___________ of Light

10. The resultant displacement at that point is equal to the vector sum of the displacements due to all the waves
(a) Scalar Sum
(b) Vector Sum
(c) Scalar Product
(d) Vector Product

11. Coherent Sources of light is a Conditions for obtaining a _____________ Pattern

12. Insertion of transparent sheet in path of one of the two interfering beams: _______ fringes including central bright band is shifted by ∆x
(a) Odd Numbered
(b) Odd Numbered
(c) All
(d) None of the

13. The pattern containing alternate bright and dark bands which are steady (i.e. constant with respect to ______, _____ and ________) is called “Steady Interference Pattern”

14. ________ is an optical device which consists of two right angled thin prisms place base to base, having a very large refracting angle (about 179°) and the other two angles are about 0.5° each and it is used to produce two virtual coherent sources

15. The phenomenon of bending of light around the corners of an obstacle or an aperture into region of geometrical shadow of obstacle is called _______ of Light

16. Principle of Superposition: When two or more waves traveling through a medium, arrive at a point simultaneously, each wave produces its own _______ at that point independently

17. When two light waves, arrive at a point and crest of one wave coincides with trough of another wave (or trough of one wave coincides with crest of another wave), then the phenomenon is called _______________

18. The phenomenon of ____________ of light is due to the superposition of waves

19. When the source of light and screen are at infinite distance from the slit, the diffraction produced is called __________ Diffraction, which is obtained using convex lens

20. When the source of light and screen are at a finite distance from the slit, the diffraction produced is called _______ Diffraction

21. What is the importance of Young’s Experiment?

22. The minimum distance (linear or angular) between two objects when they can be observed as separate (just resolved) by an optical instrument is called __________ of that instrument

23. The ability of the optical instrument to produce distinct and separate images is called __________ of that instrument

24. When Path Difference of two light waves at a point is nλ, then the brightness at that point is ___________

25. When two light waves interfere, the resultant wave is ______ wave of same frequency

26. The _________ of the limit of resolution is known as “Resolving Power” of that instrument

27. When two light waves have phase difference either zero or constant, they are called _____ sources of light

28. When Phase Difference of two light waves at a point is (2n – 1)π, then the brightness at that point is ___________

29. Insertion of transparent sheet in path of one of the two interfering beams: There is no change in fringe _____ due to shifting

30. Light waves are diffracted only when the size of obstacle or aperture is _______ to the wavelength of light

```ZoomPhysics - A Physics learning software (Windows) for students preparing for Engineering & Medical Entrance Exams FREE Download {132 MB}```

## Answers: MCQs On Interference And Diffraction Of Light

01. Just Resolved
02. central maxima
03. (d) independent of
04. Just
05. Rayleigh’s Criterion
06. Well, Completely
07. True
08. Monochromatic
09. Interference
10. (b) Vector Sum
12. (c) All
13. position, time, intensity
14. Biprism
15. Diffraction
16. displacement
17. Destructive Interference
18. Interference
19. Fraunhofer
20. Fresnel
21. It was the first experiment to observe interference of light. It proved the wave nature of light. It can also be used to determine wavelength of monochromatic light. All the conditions necessary to obtain steady state interference pattern can be satisfied
22. Limit of Resolution
23. Resolving Power
24. Maximum {Bright Point}
25. harmonic
26. reciprocal
27. coherent
28. Minimum {Dark Point}
29. width
30. comparable