Chapter 29, Problem 8Q

To determine

Why free moving electrons cannot leave metal surface.

Explanation of Solution

Conduction electrons are free to move but they cannot leave the surface of metal as when they try to leave the surface it creates a net positive charge in the metal, force of attraction between this positive charge and leaving electron is much stronger than the repulsive forces between a leaving electron and other neighbouring electrons. So energy must be supplied to remove an electron from metal surface, this amount of energy is called work function of the material.