Question

A metal acting as a thermionic emitter must have

• A. low work function and low melting point
• B. low work function and high melting point
• C. high work function and low melting point
• D. high work function and high melting point

Answer 1

The correct option is B low work function and high melting point

Thermal energy given to the charge carriers overcome the work function of the metal surface and thus flow of charge carriers takes place from the metal surface. Lower the work function of the metal, more easily will be the thermions emitted. Also, the melting point of the metal must be very high so that it does not melt even at high temperature.

Hence the metal acting as a thermionic emitter must have low work function and high melting point.