Consider a beam of electrons (each electron with energy E0) incident on a metal surface kept in an evacuated chamber. Then Chapter Eleven
When a beam of electrons (each with energy E0) is incident on a metal surface, electrons can be emitted as there will be collision between the electrons.
If the collision is elastic, electrons are emitted with energy E0.
If the collision is inelastic, some energy is used in liberating the electrons from the metal surface and electrons are emitted with energy less than E0.
Hence, maximum energy of liberated electrons is E0.