Compton Scattering experiment help

[RaZi3l]

Homework Statement

What parts of the Compton Collision experiment can be explained using classical models and which require the "photon" model?

Anyone can help me with this question?

 

[arunma]

Hmm...I'm not sure what you mean. I know there are a couple of ways to treat Compton scattering. The first way involves finding the frequency (or wavelength) shift in the Compton-scattered photon. This can be done by imposing momentum and energy conservation on the system as well as the following relations for the photon:

$$E = hf$$
$$E = pc$$

That's where you get the following equation:

$$\lambda' - \lambda = \dfrac{h}{mc}(1-cos(\theta))$$

The energy-frequency relation for a photon is basically how we relate the wave and particle theories of light. The energy-momentum relation is pretty much just relativity with the understanding that the photon is a massless particle. So I guess that even here we're using "classical" and "photon" models. Depending on your definition of quantum mechanics though, even treating the photon as a particle is still "classical physics."

Now you can also use quantum field theory to write out the Feynman diagram for Compton scattering (since it's a quantum electrodynamic process). That's how you can calculate the scattering cross-section for this process. It's pretty important for us in astrophysics, since scattering works differently in the Thompson regime (low energy) and Klein-Nishina regime (high energy). I don't know if you're supposed to worry about that though.

You could probably work out the energy change in a photon by treating it as simple classical scattering. But to turn that into a frequency you'd need to use the "photon model."

 

[RaZi3l]

thx for the reply.
Photon model means that treating it as particle, while classical model means that it was treated as wave.

 

[Count Iblis]

The Thompson cross section mentioned by arunma is a "classical" result, you can derive it using the Maxwell equations.