# Compton Scattering Question

1. Oct 14, 2007

### zing478

1. The problem statement, all variables and given/known data
If the maximum energy transferred to an electron during Compton Scattering is 50KeV, what is the wavelength of the incident photon?

2. Relevant equations
$$\lambda$$' - $$\lambda$$$$_{o}$$ = h/(Me*c)(1-cos$$\theta$$)

3. The attempt at a solution
We know that the maximum energy transfer for compton scattering occurs when:
$$\theta$$ = 180
$$\phi$$ = 0

So when $$\theta$$=180
$$\lambda$$' - $$\lambda$$$$_{o}$$ = 0.00486nm

Everything I've tried looking up involves the scattered photon as well (like the momentum, energy, wavelength equations)

Any tips on where to look/where I can go next?

2. Oct 14, 2007

### Staff: Mentor

Apply the conservation of momentum and energy.

One has the energy of the electron, from which one can obtain the momentum.

pph = E/c

3. Oct 14, 2007

### zing478

I'm still stuck at finding the momentum of the electron. I know it's going to have 50 000ev of Kinetic Energy, but I'm not sure how to relate it to momentum.

4. Oct 14, 2007

### Staff: Mentor

One could do it either classically, e.g. p = mv and KE = 1/2 mv2 = 1/2 p2/m, where m is the rest mass, or relativistically where m = $\gamma$mo, taking into account the change in mass with velocity.

50 keV is ~0.1 of the rest energy 0.511 MeV.

5. Sep 2, 2010

### ini

I can't solve this problem too!!! Please help me!!! I am taking exams next week and i 'm supposed to know what happens!!! my prof gave us a little help by saying these:

1). 1239.8/E=.... (and i think from this we have λο)
2). ΔΕ -> Εφ=Εφ'+Εmax(e) -> 50keV=Εφ-Εφ' (where Eφ=photon's energy)
3) θ=π since (1-cosθ)=max

Can anybody help???????