We were redoing a house, and he had put in all the plastic piping, you know, and I was gonna test the joints, these are supposed to be glued together, with his pipe glue, right?
When a photon hits this junction of materials in the photodiode, called a p-n junction, an atom's electron absorbs the photon's energy, and as a result, it jumps up to a higher energy state and leaves the atom.