# Engineering Physics Questions and Answers – X-Rays and Compton Effect

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

1. What is the relation between the interaction parameter, ‘b’, and atomic radius, R, for the Compton Effect?
a) b > R
b) b ≈ R
c) b < R
d) No relation between b and R

Explanation: If b ≈ R, the incident photons are scattered by the electron of the atom and the electron itself gets scattered. This phenomenon is known as the Compton effect.
If b < R, the photon is directly converted into an electron-positron pair, known as pair production.
If b > R, it means the interaction parameter is greater than the atomic radius. In this case, the electron is ejected by the photon and it is known as the Photoelectric effect.

2. The Compton effect can be explained on the basis of __________
a) Wave nature of light
b) Quantum theory of light
c) Ray optics
d) Wave optics

Explanation: The quantum theory of light i.e., the photon concept successfully explained the Compton effect. The wave theory predicts the scattered radiation will have the same wavelength.

3. What kind of photon is required for the Compton effect to occur?
a) Visible Light Photon
b) X-ray Photon
c) Infrared
d) UV Photon

Explanation: When a γ-ray and X-ray Photon passes close to an atomic nucleus, the scattered radiation have radiations of smaller wavelength along with the one of the same wavelength.

4. The expression for Compton shift is _________
a) $$\frac{h}{m_0 c}cos\theta$$
b) $$\frac{h}{m_0 c}(1 – cos\theta)$$
c) $$\frac{h}{m_0 c}sin\theta$$
d) $$\frac{h}{m_0 c}(1 – sin\theta)$$

Explanation: The expression $$\frac{h}{m_0 c}(1 – cos\theta)$$ is the expression for the Compton shift. It gives the expression for the change in wavelength that occurs during Compton effect.

5. Visible Light rays can show Compton effect.
a) True
b) False

Explanation: Compton effect cannot be observed for light rays. It is so because the Compton shift observed for visible light rays is about 0.001% which is undetectable.
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6. X rays of wavelength 0.15 nm are scattered from a block of carbon. What is the wavelength of X-rays scattered at 00?
a) 0.15 nm
b) 0.154 nm
c) 0.165 nm
d) 0.178 nm

Explanation: As we know, $$\Delta\lambda = \frac{h}{m_0 c}(1 – cos\theta)$$
Here, as cosθ = 1, Δλ = 0
Hence, λ’ = 0.15 nm.

7. X-rays with wavelength 0.1 nm are scattered from a carbon block. The scattered radiations are viewed at right angles to the direction of incident beam. What is the Compton shift?
a) 0.0014 nm
b) 0.0024 nm
c) 0.0034 nm
d) 0.0044 nm

Explanation: As we know, $$\Delta\lambda = \frac{h}{m_0 c}(1 – cos\theta)$$
Here, cosθ = 0. Therefore,
Δλ = $$\frac{2h}{m_0 c}$$
= 0.0024 nm.

8. In Compton scattering, if the incident photon has a wavelength of 0.2 nm and Φ = 90°, the angle at which recoil electron appears is ___________
a) 30.12°
b) 38.46°
c) 44.57°
d) 53.12°

Explanation: We know, tanθ = $$\frac{\lambda sin⁡\Phi}{\lambda^{‘}-\lambda cos⁡\Phi}$$
= 2 X 10-10/(2.204 – 2) X 10-10
= 2/2.024
= 0.9980
Θ = tan-10.9980
= 44.57°.

9. The following graph is seen for which angle?

a) 30°
b) 45°
c) 90°
d) 120°

Explanation: The given figure shows the variation of intensity with wavelength in Compton scattering when the angle θ is equal to 90°.

10. Identify X in the expression for Kinetic energy of recoil electron: $$k_e=hv(\frac{x(1-cos⁡\theta)}{1+x(1-cos⁡\theta)})$$.
a) hv/mo
b) hv/moc
c) hv/moc2
d) hv/c2

Explanation: In the given expression, x = hv/moc2. This is the expression for the Kinetic Energy of recoil electron. It is derived by Einstein’s mass energy relation and the expression for Compton shift.

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