Question

Can someone explain these answers. Thank you!

31) You perform Compton scattering experiments with X-rays of a fixed wavelength. In one
experiment you scatter the X-rays from free electrons. In the second experiment you scatter the
X-rays from protons instead. For X-rays scattered under a given angle, the wavelength change
A) will be larger for scattering from protons.
B) will be the same for both cases.
C) will be larger for scattering from electrons.
D) depends on the actual wavelength of the X-rays.
Answer: C
Diff: 1 Var: 1 Page Ref: Sec. 30-4

32) What happens to the frequency of the scattered X-rays beam as the scattering angle in the
Compton effect decreases?
A) It stays the same.
B) It decreases.
C) It increases.
D) Not enough information
Answer: C
Diff: 2 Var: 1 Page Ref: Sec. 30-4

Answer 1

For Compton scattering, scattered wavelength is given as

h is the Planck's constant, m is the mass of the scatterer, c is the velocity of light and is the angle of scattering.

31) Compton scattering is first performed with free electrons and then with protons.

We see that the Compton shift is inversely proportional to the mass of the scatterer.

Mass of an electron is much lighter than that of the proton. So, scattering will be larger for electron.

Option C is correct.

32) Writing the Compton shift in terms of frequency we have

As the scattering angle decreases, increases and the term on the denominator decreases. As a result the frequency increases.

Option C is correct.