Explain photoelectric effect on the basis of Einstein theory.

Explanation

The ejection of electrons from a metal surface, when the radiations of suitable frequency strikes the metal surface is called photoelectric effect.
Explanation using Einstein.s quantum theory:
1) To explain photoelectric effect, Einstein utilised Quantum theory.
2) When a photon strikes metal surface, it uses some part of its energy to eject the electron from the metal atom. The remaining part of the total energy is given to the ejected electrons in the form of kinetic energy.
Hence we ́can write `hv=W+KEimplieshv=hv_(0)+(1)/(2)m_(e)V^(2)`
where hv = energy of photon, `=v_(0)`= Threshold frequency, `m_(e)` = mass of electron
W = energy required to overcome the attractive for electron in the metal (work function)
KE= kinetic energy of ejected electron, V= Velocity of ejected electron.
3) If a photon of sufficient energy struck the metal surface and could eject the electron. But if a photon has insufficient energy, it cannot eject the electron from the metal.
eg. : A photon, of violet light [high frequency] can eject the electrons from the surface of potassium but a photon of red light slow frequency cannot eject the electrons.