"To emit a free electron from a metal surface a minimum amount of energy must be supplied" For metal A (tungsten) - work function is 4.52 eV for metal B (thoriated tungsten) it is 2.6 ev, for metallic (oxide coated tungsten) it is 1 eV Which will you prefer as a good electron emitter and why?

Explanation

Work function for metallic oxide coated tungsten is small (1ev.) Hence this material is good elec tron emitter