5CH - Quantum theory of light

If light and other electromagnetic radiations are made of photons then each photon must have an energy associated with it. This energy is E = hf. Thinking back to the photoelectric effect, we know that some materials will eject electrons when you shine radiation on them. The minimum energy required for this to happen is called the work function of the material. If a photon has an energy equal to this work function then it will cause an electron to be ejected to the surface. If the photon has an energy greater than the work function then the remaining energy will converted into kinetic energy of the photoelectron produced.