Interference and Diffraction MCQ Questions and Answers for Practice

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