Question

1. What is thermionic emission ?
2. Name the unit in which the work functions of a metal is expressed ?

Answer 1

(i) Thermionic emission :-

1. Thermionic emission is the liberation of electrons from an atom by virtue of the temperature.
2. This occurs because the thermal energy given to the charge carrier overcomes the work function of the material.
3. Due to this result emission of free electrons from the metal surface is called thermionic emission and this type of metal surface is called a thermion emitter.

(ii) Unit of the work functions of a metal:-

1. The minimum energy required for a free electron to come out of the metal surface is called the work function of that metal.
2. S.I. unit of work function is joules and other popular unit is electron-volts $\left(eV\right)$.