Photoelectric effect
The energy of a photon causing the photoelectric effect is found through , where  is Planck's constant,  J·s,  is the frequency of the electromagnetic wave,  is the kinetic energy of the photoelectron and  is the work function for the metal. If the photon has a lot of energy, Compton scattering (~ thousands of eV) or pair production (~ millions of eV) may take place.