Recall: According to the photoelectric effect, an electron can be ejected from the surface of a metal if it's hit with photons of sufficient energy. The kinetic energy (KE) of the ejected electron is related to the energy of the photon (Ephoton) hitting the metal surface by this equation:
where φ = work function of the metal, which is the minimum energy of a photon that is needed to eject an electron. The threshold frequency, v0, of a metal is the minimum frequency needed to eject an electron and is given by:
where h = Planck's constant (6.626 × 10–34 J • s).