# Engineering Physics Questions and Answers – Compton Effect

This set of Engineering Physics Multiple Choice Questions & Answers (MCQs) focuses on “Compton Effect”.

1. Which of the following is the characteristic of a black body?
a) A perfect absorber but an imperfect radiator
b) A perfect radiator but an imperfect absorber
c) A perfect radiator and a perfect absorber
d) A perfect conductor

Explanation: When the radiations are made to pass through a black body, it undergoes multiple reflections and is completely absorbed. When it is placed in a temperature bath of fixed temperature, the heat radiations will come out. Thus a black body is a perfect absorber and a perfect reflector.

2. The energy distribution is not uniform for any given temperature in a perfect black body.
a) True
b) False

Explanation: At different temperatures, when a perfect black body is allowed to emit radiations, then the distribution of energy for different wavelengths at various temperatures is not uniform.

3. Rayleigh-Jean’s law holds good for which of the following?
a) Shorter wavelength
b) Longer wavelength
c) High temperature
d) High energy

Explanation: According to this law, the energy distribution is directly proportional to the absolute temperature and is inversely proportional to the fourth power of the wavelength. Therefore longer the wavelength, greater is the energy distribution.

4. Wien’s displacement law holds good only for shorter wavelength.
a) False
b) True

Explanation: This law states that, the product of the wavelength, corresponding to maximum energy and the absolute temperature, is constant. If ʎ is less, then 1/ʎ will be great. Therefore e(hc/ʎKT) will be great.

5. Which of the following does not affect the photon?
a) Magnetic or electric field
b) Light waves
c) Gravity
d) Current

Explanation: Photons have no charge. They can interact with charged particles but not with themselves. This is why photons are neutral and not affected by magnetic or electric fields.
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6. What is Compton shift?
a) Shift in frequency
b) Shift in charges
d) Shift in wavelength

Explanation: When a photon collides with an electron at rest, the photon gives its energy to the electron. Therefore the scattered photon will have higher wavelength compared to the wavelength of the incident photon. This shift in wavelength is called Compton shift.

7. Compton shift depends on which of the following?
b) Nature of scattering substance
c) Angle of scattering
d) Amplitude of frequency

Explanation: From the theory of Compton effect it is deducted that change in wavelength
Δʎ = h/mc (1-cosɵ). This equation shows that the change in wavelength is independent of the incident radiation as well as the nature of scattering substance. The shift depends only on the angle of scattering.

8. Which of the following is called as non-mechanical waves?
a) Magnetic waves
b) Electromagnetic waves
c) Electrical waves
d) Matter waves

Explanation: The waves which travel in the form of oscillating electric and magnetic waves are called electromagnetic waves. Such waves do not require any material for their propagation and are called non-mechanical waves.

9. Which of the following is associated with an electron microscope?
a) Matter waves
b) Electrical waves
c) Magnetic waves
d) Electromagnetic waves

Explanation: The waves associated with microscopic particles when they are in motion are called matter waves. Electron microscope makes use of the matter waves associated with fast moving electrons.

10. A radio station broadcasts its programme at 219.3 metre wavelength. Determine the frequency of radio waves if velocity of radio waves is 3×108 m/s.
a) 7.31×10-7 Hz
b) 1.954×10-6 Hz
c) 1.368×106 Hz
d) 6.579×1010 Hz

Explanation: ʎ = velocity/frequency
Frequency = velocity/ʎ
Therefore, frequency = 1.368×106 Hz.

11. Calculate the de-Broglie wavelength of an electron which has been accelerated from rest on application of potential of 400volts.
a) 0.1653 Å
b) 0.5125 Å
c) 0.6135 Å
d) 0.2514 Å

Explanation: de-Broglie wavelength = h/√(2×m×e×V)
De-Broglie wavelength = (6.625×10-14)/√(2×9.11×10-31×1.6×10-19×400)
Wavelength = 0.6135 Å.

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