S N Physics Expert

  Electron emission Introduction The phenomenon of emission of electrons from the surface of a metal is called electron emission. Electron emissions are  of following types : Thermionic emission Photoelectric emission Field emission or Cold cathode emission Secondary emission Thermionic emission It is the phenomenon of emission of electrons from the metal surface when heated  suitably.  The energy required for emission of electrons from the metal surface is being supplied by thermal energy.  The emitted electrons are called thermal electrons or thermions.  The number of thermions emitted depends on the temperature of the metal surface. Photoelectric emission The phenomenon of emission of electrons from the surface of metal when light radiation of suitable frequency falls on it  is called Photoelectric effect.  The energy to the free electrons for their emission is being supplied by light Photons.  The emitted electrons are called photoelectro...