Ultraviolet light is incident on metals P, Q and R, having work functions , and respectively. (a)…

Ultraviolet light is incident on metals P, Q and R, having work functions $8\text{ eV}$, $2\text{ eV}$ and $4\text{ eV}$ respectively. (a) Which metal has lowest threshold frequency for photoelectric effect? (b) For which metal is the value of $E_{\max}$ minimum? (Note: $E_{\max}$ is maximum kinetic energy of the emitted photoelectrons.)