Why does PS II require electrons from water?

A Work function of a metal is the a. energy required by an electron to get absorbed in the metal surface. b. minimum energy required by an electron to escape from the metal surface. c. energy required by an electron to be retained in the metal surface. d. maximum energy required by an electron to escape from the metal surface. B. Write Einstein's Photo-Electric Equation and explain the terms in it. C. All photo electrons are not emitted with the same energy as the incident photons. Why?

______water heater does not require electricity.

Why does sky appear blue?