1. The Compton Effect
Topic 14.3

2. Outcomes
You will explain, qualitatively and quantitatively, the Compton Effect as another example of wave-particle duality, applying the laws of mechanics and of conservation of momentum and energy to photons.

3. Compton’s Experiment
He fired x-rays at a thin piece of foil, similarly to the photoelectric effect, he found that electrons from the foil were emitted when x-rays collided with them
He found the energy and momentum gained by the emitted electrons was equal to the energy and momentum lost by the x-rays

4. Wave-Particle Duality
Compton demonstrated that x-rays upheld the laws of conservation of energy and momentum in collisions with electrons:
Photons loose energy and momentum in their collisions with electrons that is equal to the energy and momentum gained by the emitted electron
These collisions are ELASTIC (no loss of kinetic energy)
This means that EMR photons must have momentum, and therefore behave like particles

5. Calculating momentum The momentum can be calculated using:
The change in wavelength/frequency was related to the change in momentum of the electron. The photon behaves exactly like a particle colliding with an electron!
Collision questions can therefore be done between electrons and photons (where the momentum of the photon is p=h/ and the electron is p=mv)

6. One more Equation
Compton also derived the following relationship between the change in the wavelength of the scattered photon and the direction in which the scattered photon travels:

7. Sample Problem
An X-ray photon of wavelength nm scatters at an angle of 30°. Calculate the wavelength of the scattered photon.

8. Homework
Concept/Calculation Qs:
p. 724 #1
p. 725 #1-7