Hi, After searching the forum I did not find an answer to my question, so here goes. In the classical theory a photon can only eject a photo electron when the energy of the photon is greater than the binding energy of the electron. This is only possible with bound electrons as some of the recoil momentum has to be taken over by the nucleus. The photoelectric effect was observed with visible light and a metal. I assume that the photo electrons emitted from a metal by visible light are actually electrons originating from the conductance band (CB) as the photon energy is quite low. This also means that the recoil momentum is actually taken over by the crystal lattice of the metal. Is this correct? When the incident photons far greater energy and we still try to eject photoelectrons from a metal what will happen? I think that no electrons from the CB will be ejected and, depending on the energy, bound electrons will be ejected because the recoil momentum can now only be taken over by the nucleus. Or will there also be electrons emitted from the CB (now with far greater kinetic energy)? Is related to the atomic cross-section of the photoelectric effect? Someone with some input?