In which of the following, emission of electrons does not take place\

Question

Professor PC Thomas Classes · Answer

(b) : Thermionic emission : When a metal is heated to a high temperature, the free electron gain kinetic energy and escape from the surface of the metal.\ Secondary emission : When an electron strikes the surface of a metallic plate, it emits other electrons from the surface. Photoelectric emission : Emission of electrons from the metal surface on irradiation with radiation of suitable frequency. $X$-rays emission : They are due to transitions in the inner energy levels of the atom.\