To emit an electron from the metal surface the photon needs energy which is equal to the sum of the kinetic energy of electrons and energy needed to remove the electron.
So photoelectric equation is:
Energy of photon = KE of emitted electron + energy needed to emit the electron.
h = W + E
- h = Planck’s constant
- v = frequency of photon
- W = work function
- E = kinetic energy of electrons