I have seen many 'photoelectric effect vs compton effect' Questions in this and other forums, but i am still not convinced. I can see how photoelectric effect points to the particle nature of light. But i don't see how compton effect as a separate experiment is needed to confirm this. The only difference i see is that in PE, the energy of the photon is completely absorbed by the e, while in CE the photon is scattered with some energy remaining. So aren't the CE and PE two particular cases of the same phenomenon? And why does one occur in bound electrons and the other in free electrons. I have also read that CE occurs in bound electrons when the energy of incident radiation is high. why doesnt the excess energy go to the KE of electron instead of getting scattered as a photon?