In the context of interaction of photons (with energies from around visible light and upwards) and the electrons of solid matter. I've read that at the lower energy levels that the photoelectric effect is more likely to occur during such an interaction and that Compton scattering is more likely for higher photon energies like x-rays. (.... and pair production at even higher energies). I was just wondering why this is. Looking at it from a simplistic point of view I would have expected the opposite. That is, I would have expected that the higher energy photons would have been more likely to completely knock an electron out of the solid (PE effect) and that the lower energy photons would have been more likely to just make the electrons recoil as in Compton scattering. Any simple explainations?