# Compton Effect

1. Feb 22, 2014

### MostlyHarmless

I'm pretty sure this is a fairly obvious question, but I can't ever be sure..

So, if a photon is "scattered" 180 degrees. Its not being scattered at all, correct? So, then the energy of the "recoiling electrons" would be 0.

It makes sense mathematically if I'm doing it right.

${\lambda}_2-{\lambda}_1={\frac{h}{m_ec}}(1-cos{\theta})$

$h$ is Planck's constant, $m_e$ is electron mass, c, speed of light. If theta is 180, change is wavelength is 0, so then there is no scattering? Is the all consistent?

The reason I'm so hesitant, is because this is a homework problem, and the only one assigned dealing with recoiling electrons, so I figured it would be... less trivial.

Note: Excuse the lack of homework template, I'm posting this off of my phone, which does not give me the template.

2. Feb 22, 2014

### George Jones

Staff Emeritus
Not correct.

What is cos(180)?

3. Feb 22, 2014

### MostlyHarmless

>.< Doh. That's what I get for just punching it my calculator and then not writing it down.

hen it says, 180, its "scattering" back in the direction if the incident photon?

So the change in wave length should be $2h/(m_ec)$?

4. Feb 22, 2014

### vela

Staff Emeritus
Right. The angle $\theta$ is the angle by which the photon is deflected.