Concept:The minimum energy required to release an electron from a metal surface is called the work function.
Explanation:When electromagnetic radiation of suitable frequency strikes a metal surface, each photon transfers energy to an electron.
The electron can escape only if the photon energy is at least equal to the minimum energy needed to overcome the attractive forces holding it in the metal.
This minimum energy is fixed for a given metal and is called the work function.
It is usually denoted by
ϕ or
W.
Ionization energy is the energy needed to remove an electron from an isolated atom, not from a metal surface.
Planck's constant is a physical constant, not an energy value.
Therefore, the correct term is the work function.
Answer:C. work function