E = energy, h = Planck's constant, v= lowest frequency of a photon that expels an electron from the metal, f = work function

  The photoelectric effect, first elucidate by Einstein, describes what happens when light is incident on a metal.

  The energy E of an electron emitted from a metal by a photon of energy hv given above. The constant f is called the work function, and is defined as the minimum work required to remove an electron from the metal.