 Solution

The incident photon rate is ${\dot{N}}_{\gamma }=P/(hc/\lambda )\simeq 2.30\times 10^{15}{\mathrm{s}}^{-1}$. The stated quantum efficiency is $\eta =0.005$, so the emitted electron rate is $\eta {\dot{N}}_{\gamma }\simeq 1.15\times 10^{13}{\mathrm{s}}^{-1}$. If all emitted electrons are collected, the photocurrent magnitude isThe light power controls the number of events; the work function already determined the kinetic energy per emitted electron and should not be subtracted from the photon energy when counting incident photons. Incomplete collection would reduce the measured photocurrent below this value.