Ultraviolet light of wavelength 310 nm is directed at three...

The energy of the incident photon is given by $E = \dfrac{hc}{\lambda}$

Substituting the given values:

$E = \dfrac{1240 \text{ eV nm}}{310 \text{ nm}} = 4.0 \text{ eV}$

For photoelectric emission to take place, the energy of the incident photon must be greater than the work function of the metal ($E > \phi$).

For metal P: $4.0 \text{ eV} > 2.2 \text{ eV}$ (Emission occurs)

For metal Q: $4.0 \text{ eV} > 3.5 \text{ eV}$ (Emission occurs)

For metal R: $4.0 \text{ eV} < 4.8 \text{ eV}$ (No emission)

Thus, photoelectrons will be emitted from plates P and Q only.

Answer: P and Q only