Einstein’s Photoelectric Equation :
According to Einstein, light of frequency consists of a shower of photons, is of energy . When a photon of light of frequency is incident on a metal, a part of the energy acquired by the electron is used to pull out the electron from the surface of the metal and the rest of it is utilized in imparting K.E. to the emitted electron.
Let, be the energy spent in extracting the electron from the emitter and the K.E. of the photo-electron.