Question

Suppose a beam of electrons with each electron having energy e0 incident on a metal surface kept in an evacuated chamber. Then,

Answer 1

Your question is incomplete.

But depending on the energy of the electrons, if the energy of the electron is greater than the threshold energy of the metal, then a photon is ejected. If the energy of the electron is lesser than threshold energy, then no photon is ejected.

Hope it helps.