- #1
ChessEnthusiast
- 115
- 3
Homework Statement
A photon with the length of lambda hits a cathode perpendicularly to its surface. As a result, an electron leaves its surface perpendicularly to the direction of the photon. How much momentum was transferred from the photon to the cathode? The work function of the cathode is W.
2. The attempt at a solution
1. I calculate the speed of the electron:
[tex]v = \sqrt{ \frac{2hc}{\lambda m_e} - \frac{W}{m} }[/tex]
2. The momentum of the photon:
[tex]p_{photon} = \frac{h}{\lambda}[/tex]
3. The momentum of the electron:
[tex] p_{electron} = m \sqrt{ \frac{2hc}{\lambda m_e} - \frac{W}{m} } [/tex]
Now, I am stuck and don't know what to do because of this 90 degree angle.