# Homework Help: What wavelength of photons are needed to produce 30keV electrons in a compton scatter

1. Sep 9, 2009

### KingNothing

1. The problem statement, all variables and given/known data
56. What wavelength of photons are needed to produce 30 keV electrons in a compton scattering?

2. Relevant equations
$$E=\frac{hc}{\lambda}$$

3. The attempt at a solution
This question throws me off because I was under the impression that compton scattering didn't produce any electrons, but simply deflected them. It also confuses me because I assume it's asking "What photons will produce electrons with total energy of 30-keV?" However, electrons have that much energy in rest mass alone.

Can anyone interpret this better?

2. Sep 9, 2009

### rock.freak667

Re: What wavelength of photons are needed to produce 30keV electrons in a compton sca

Not sure what compton scattering is, but I'd find the velocity of the electrons from their energy and and then use the de Broglie wavelength formula

$$\lambda = \frac{h}{mv}$$

3. Sep 9, 2009

### KingNothing

Re: What wavelength of photons are needed to produce 30keV electrons in a compton sca

With all due respect, your suggestion does not make sense in the context of what we've discussed. We've discussed compton scattering, and have not discussed de Broglie wavelengths.

4. Sep 10, 2009

### kuruman

Re: What wavelength of photons are needed to produce 30keV electrons in a compton sca

Here is my interpretation:

Assume that you have an electron at rest. An incoming photon Compton scatters off it and the electron acquires a kinetic energy of 30 keV. What is the initial wavelength of the photon?

Last edited: Sep 10, 2009