1. The problem statement, all variables and given/known data 2. Relevant equations Einsteins photon momentum: p=h/wavelength (rearrange to get de broglie wavelength) 3. The attempt at a solution I am quite new to all this quantum physics stuff. First of all where is the momentum of the electron reffering to its angular momentum when it is orbiting? Can anyone explain this further to me. I think I need an equation here that relates the momentum to kinetic energy, I can't find anything like that.