hi... i found a number of similar thread posing the same question but i didn't get the answer i was looking for, so i am asking it again. Basically, as far as i have understood photoelectric effect is about absorption of a photon by an electron and the extra energy converted to its kinetic energy; while in case of Compton effect there is collision (or scattering), not complete absorbtion, and the recoil. The two are about interaction of one photon-and-one electron, but with different energies of the photon, still in one, electron completely absorbs the photon and gets kinetic energy; while the other doesn't convert the whole energy to kinetic energy instead produces a photon of greater wavelength. How really is the electron able to decide when to absorb a photon and when to scatter it; how does the electron get to know the energy of the photon before interacting with it (i.e. absorbing); does it sense the energy and decides what to do next with it?? What really happens?? (please pardon me if the questions sound stupid and irrelevant).