What is the difference between the two ? Maybe that in the photoelectric effect all of the energy of a photon is absorbed by the electrons ? Is that it ? In Compton scattering, only part of the energy is absorbed hence there is a photon of lower frequency emitted ! OR Maybe in the two processes we use e.m waves of different frequencies ? Here is another thought : Which one of them is the closest of being the exact opposite of the production of x-rays ? To answer the above query, I need to know : Are the electrons (from the bremsstrahlung radiation) decelerated to exactly zero velocity (after striking the metal surface) OR are they reflected (eleastically/inelastically) from the metal surface ?