Interference and Diffraction MCQs Quiz Multiple Choice Questions & Answers

1. Colors in thin films are because of

1. Dispersion
2. Compton effect
3. Interference
4. Diffraction

2. Diffraction due to circular aperture If a light passes through a small pinhole, and incident on a screen. What will be observed on the screen?

1. A sharp bright point of the width equal to width the pinhole
2. A bright point of the width equal to width the pinhole but of less intensity
3. A bright ring at the centre surrounded by alternate dark and bright rings
4. A diffused bright point

3. Diffraction is special type of

1. Reflection
2. Refraction
3. Interference
4. Polarization

4. Extended source is needed in

1. Youngs double slit experiment
2. Bi prism Experiment
3. Newtons Ring Experiment
4. None of them

5. Find the maximum value of resolving power of a grating 3 cm wide having 5000 lines per cm, if the wavelength of light used is 5890 A^o.

1. 40000
2. 45000
3. 4500
4. 5000

6. For all transparent material substances, the index of refraction

1. is less than 1
2. is greater than 1
3. is equal to 1
4. Could be any of the given answers; it all depends on optical density

7. Fraunhofer diffraction at a Plane Grating. What is the meaning of grating element for a diffraction grating?A It is the width of a single slit

1. It is the width of the opaque space
2. It is the distance between two slits
3. It is the width of diffraction grating

8. Fraunhofer diffraction is observed when

1. Only screen is placed at finite distance
2. source is placed at finite distance
3. neither source nor screen is at finite distance
4. None of these

9. Fresnels type diffraction is observed when

1. Only screen is placed at finite distance
2. Only source is placed at finite distance
3. Both source and screen are at finite distance
4. Neither source nor screen is at finite distance

10. Fringe spacing is defined as the distance between two Consecutive

1. Crests
2. Bright fringes only
3. Dark fringes only
4. Bright or dark fringes

11. How the intensity of secondary maxima varies in case of Fraunhofer diffraction pattern for single slit?

1. Intensity of secondary maxima decreases on either sides
2. Intensity of secondary maxima remains constant on either side
3. Intensity increases and decreases alternately
4. Intensity of secondary maxima increases on either sides

12. If we narrow the distance between two slits in Youngs experiment the fringes width

1. Increases
2. Decreases
3. Remains same
4. becomes zero

13. If you look perpendicular at thin film and move yourself away from the film (staying perpendicular to the film), you will notice

1. Reflected light becomes brighter and brighter
2. Reflected light becomes darker and darker
3. Reflected light alternates between darker and brighter
4. None of the Above

14. In a longitudinal wave

1. The particles move parallel to the direction of the wave motion.
2. The particles move perpendicular to the direction of the wave motion.
3. Energy causes the particles to move forward with the wave.
4. Energy is propagated by crests and troughs.

15. In a Youngs double-slit experiment the center of a bright fringe occurs wherever waves from the slits differ in the distance they travel by a multiple of

1. a fourth of a wavelength
2. a half a wavelength
3. a wavelength
4. three-fourths of a wavelength

16. In case of thin film of non-uniform thickness, when illuminated with white light, the film appears colored. This is due to change of what factor?

1. Conditions for path difference at different points of film
2. Change in optical path difference at different points of film
3. Thickness of film is different at different points of film
4. All of above

17. In diffraction Fraunhofer diffraction pattern due to single slit central maxima is formed at center because

1. Lens focuses all the diffracted rays at the centre of the slit
2. Slit focuses all the diffracted rays at the centre of the slit
3. Light rays focused at the centre of the screen undergo constructive interference
4. Slit and lens both combined focuses the rays at the centre of the slit

18. In diffraction pattern of monochromatic light the bright bands formed are

1. of uniform intensity
2. of non-uniform intensity
3. of uniform width
4. is of different colors

19. In Fraunhofer diffraction pattern for single slit, a central maximum is obtained when angle of diffraction q is equal to zero. What it actually indicates?

1. All the diffracted rays are parallel and focused by slit at a single point on screen
2. All the diffracted rays are perpendicular and focused by slit at a single point on screen
3. The rays are diffracted by the slit in all the directions
4. The rays are reflected by the slit

20. In Fraunhofer diffraction wave front used is

1. Spherical
2. Circular
3. Plane
4. Conical

21. In Fraunhofer diffraction, the incident wave front should be

1. elliptical
2. Plane
3. Spherical
4. Cylindrical

22. In Fresnel diffraction

1. source of light is kept at infinite distance from the aperture
2. source of light is kept at finite distance from the aperture
3. Convex lens used
4. aperture width is selected so that it can acts as a point source

23. In interference experiment, by keeping all other parameters constant, if you see the thin film interference from different angles, you will observe

1. Uniform illumination of screen
2. Uniform darkness on the screen
3. Equally spaced dark and white bands
4. Few colored bands and then general illumination

24. In interference experiment, monochromatic light is replaced by white light, we will see

1. Uniform illumination of screen
2. Uniform darkness on the screen
3. Equally spaced dark and white bands
4. Few colored bands and then general illumination

25. In Michelson interferometer semi silvered mirror is used to obtain

1. Thin film interference
2. Phase coherence
3. mono chromatic light
4. colored fringe

26. In Michelson s interferometer 100 fringes cross the field view when the movable mirror is displaced through 0.0248 mm. Calculate the wavelength of monochromatic light used

1. 5896 A^o
2. 5890 A^o
3. 4000 A^o
4. 4890 A^o

27. In Newtons ring experiment, the diameter of the 15 th ring was found to be 0.590 and that of the 5th ring was 0.336 cm. If the radius of Plano convex lens is 100 cm, compute the wavelength of light used

1. 5885 A^o
2. 5880 A^o
3. 5890 A^o
4. 5850 A^o

28. In Newtons Ring experiments, the diameter of bright rings is proportional to

1. Square root of Odd Natural numbers
2. Natural Number
3. Even Natural Number
4. Square root of natural number

29. In Newtons Ring experiments, the diameter of dark rings is proportional to

1. Odd Natural numbers
2. Natural Number
3. Even Natural Number
4. Square root of natural number

30. In Newtons rings experiment, if monochromatic source of light is replaced by another monochromatic source of higher wavelength. What will be the effect on radius (or diameter)?

1. Radius (or diameter) will decrease
2. Radius (or diameter) will increase
3. There will be no effect
4. Radius (or diameter) will remain constant but there will be more brightness

31. In Newtons rings experiment, if we reduce the radius of curvature of Plano convex lens to zero, what will be effect on Newtons rings?

1. They will become brighter
2. They will become darker
3. They will disappear
4. They will be more dense

32. In Newtons rings experiment, if we reduce the radius of curvature of PlanoConvex lens to zero, what will be effect on Newtons rings?

1. They will become more bright
2. They will become more dark
3. They will disappear
4. They will be more dense

33. In Newtons rings the central spot is

1. Always bright
2. always dark
3. can be bright or dark
4. of blue color

34. In plane transmission grating, the angle of diffraction for second order maxima for wavelength 5 x 10^-5 cm is 30 degree. Calculate the number of lines in one centimeter of the grating surface

1. 1000 lines/cm
2. 5000 lines/cm
3. 500 lines/cm
4. 10000 lines/cm

35. In reference with antireflection coating which of the following statement is true?

1. Thickness of the film should be changed for light of same wavelength but different intensity
2. Thickness of the film need not be changed for light of same wavelength but different intensity
3. Thickness of the film should be increased for light of same wavelength but higher intensity
4. Thickness of the film should be decreased for light of same wavelength but higher intensity

36. In reflected light the central fringes of Newtons ring is

1. dark
2. Bright
3. Uniform
4. Non uniform

37. In thin film of wedge shaped, by keeping all other parameters constant, if only wavelength of incident light is increased. What will be the effect on bandwidth?

1. Bandwidth increases
2. Bandwidth decreases
3. Bands will merge
4. There will not any effect

38. In wedge shaped film the interference pattern has nature

1. Parallel to the end where thickness is non-zero
2. Perpendicular to contact edge
3. Parallel to contact edge
4. Perpendicular to the end where thickness is non-zero

39. Interference in thin film is mainly because of

1. Division amplitude
2. Division of wave fronts
3. Addition of amplitude
4. Addition of wave fronts

40. Interference in thin film is mainly because of

1. Division amplitude
2. Division of wave fronts
3. Addition of amplitude
4. Addition of wave fronts

41. Interference of light is evidence that

1. The speed of light is very large
2. light is a transverse wave
3. light is electromagnetic in character
4. Light is a wave phenomenon

42. Interference pattern is observed in wedge-shaped film and bandwidth is noted. Now the angle of wedge is reduced to zero. What will be the effect on Bandwidth?

1. Bandwidth increases
2. Bandwidth decreases
3. Bands will disappear
4. There will not any effect

43. Interference pattern is observed in wedge-shaped film and bandwidth is noted. Now the angle of wedge is reduced. What will be the effect on bandwidth?

1. Bandwidth increases
2. Bandwidth decreases
3. Bands will disappear
4. There will not any effect

44. Interference pattern is observed in wedge-shaped film and bandwidth is noted. Now the thin film is replaced by the film of higher refractive index. What will be the effect on bandwidth?

1. Bandwidth increases
2. Bandwidth decreases
3. Bands will merge
4. There will not any effect

45. Interference pattern is observed in wedge-shaped film for monochromatic light. Now monochromatic light is replaced by white light. What will be the effect on interference pattern?

1. It will turn to dark
2. It will turn to bright
3. Bands will disappear
4. It will be a mixture of all colors

46. Interference pattern is observed in wedge-shaped film for monochromatic light. Now monochromatic light is replaced by white light. What will be the effect on interference pattern?

1. It will turn to dark
2. It will turn to bright
3. Bands will disappear
4. It will be a mixture of all colors

47. Light enters air from water. The angle of refraction will be

1. Greater than the angle of incidence.
2. Equal to the angle of incidence.
3. Less than the angle of incidence.
4. None of these

48. Light is

1. an electromagnetic wave
2. a form of energy visible to the human eye
3. the same type of energy as an X ray
4. all of the above

49. Light travels fastest

1. In a vacuum
2. through water
3. Through glass
4. through diamond

50. Newtons light illustrate the phenomenon of

1. Interference
2. Diffraction
3. Dispersion
4. Polarization