Einstein's equation and the potential well
If a quantum of radiation with an energy greater than the work function Eo, and therefore a frequency greater than fo, falls on a surface an electron will be emitted with some kinetic energy and escape from the surface.
The kinetic energy of the electron is then just the difference between the energy of the quantum and the work function of the metal.
This can be expressed in the following equation - called Einstein's photoelectric equation.
½ mv2 = hf - hfo
if the electrons emitted fall on a collecting electrode then the equation can also be written as:
eV = ½mv2 = hf - hfo
where V is the potential on the electrode.
If V is increased so that no more electrons reach the collecting electrode the value for the potential is called the stopping potential for that surface and radiation.
