Interference and Diffraction Multiple Choice Questions and Answers for Practice

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