Question #42617

A monochromatic light beam of frequency $\nu$ illuminates a photoelectric surface with work function $\phi$ ($h\nu > \phi$). The intensity of the beam is modulated such that the instantaneous photon flux (number of photons per unit area per unit time) is given by $n(t) = n_0 (1 + \cos \omega t)^2$, where $n_0$ and $\omega$ are positive constants. Assume that the photoelectric emission is instantaneous and the saturation photocurrent is strictly proportional to the incident photon flux. If $I_{avg}$ is the time-averaged saturation photocurrent over a long period, which of the following correctly gives the root-mean-square (RMS) saturation photocurrent $I_{rms}$ and the stopping potential $V_s$?