In a series of photoelectric emission experiments, a number of different metals were illuminated with monochromatic light of a number of different photon energies and of different intensities. The variables in the experiment were thus:

Question

(1) Work function (2) Photon energy and (3) light intensity

It was found that, for each experiment, the emitted electrons emerged with a spread of kinetic energies up to a certain maximum value. This maximum kinetic energy depends on

$\begin {array} {1 1} (a)\;1 \: only & \quad (b)\;1 \: and \: 2 \: only \\ (c)\;1\: and \: 3 only & \quad (d)\;1,2 \: and\: 3 \end {array}$