Compton Scattering Class Exercises
AP Physics
1. What is a photon?
2. Is a photon more like a particle or more like a wave?
Let’s look a little more closely at the photoelectric effect:
3. A 200 nm light wave is absorbed by the most distant electron from the nucleus in an aluminum atom.
a) How fast is the electron moving afterward?
b) After it absorbs the light, the electron has kinetic energy which means that it also has momentum.
How much momentum does the electron have?
c) Is momentum conserved when the photon is absorbed by the electron? Explain
4. How much momentum is carried by a photon of each of the following wavelengths of light?
a) 400 nm (violet)
b) 700 nm (red)
c) 125 nm (ultraviolet)
5. How would things change if the photon was not absorbed by the electron, but was scattered off of it?
(Reflection and refraction are just special types of scattering.) Conserve energy and momentum.
6. Elastic scattering of X-rays was observed and explained by the American physicist Arthur H.
Compton in 1923. Let’s investigate what he
found. The dotted line on the graph shows
measurements of X-rays that came directly
from the source. The solid line on the graph
shows measurements of X-rays that were
scattered off of a graphite block. What is
different about the data recorded in the two
lines?
7. Why would it be better to perform this experiment with X-rays instead of visible light?
8. Let’s look at a picture of this event and figure out how we would write the equations to conserve
energy and momentum.
8. A beam of x-rays with a photon energy of 1200 eV scatters off electrons in a metal.
i) What is the wavelength and frequency of these waves?
ii) Find the wavelength, frequency and photon energy after being scattered at the following angles:
a) 30°
b) 70°
c) 120°
d) 180°
9. A beam of 9.35 x 10-11 m X-rays is scattered from electrons
i) What is the frequency and photon energy for these waves?
ii) Find the wavelength, frequency and photon energy after being scattered at the following angles:
a) 30°
b) 120°
10. You observe photons scattered from a metal surface to have a frequency of 1.207 x 1017 Hz when
scattered at an angle of 150°. What was the wavelength, frequency and photon energy of the light
before it was scattered?