The Photoelectric Effect

The photoelectric effect as a phototube: light of frequency $\nu$ strikes a metal cathode and, if $h\nu$ exceeds the work function $\phi$, photoelectrons are ejected with $K_{\\max} = h\nu - \phi$ and drift to the anode under the applied voltage. Below the threshold $\nu_0 = \phi/h$ no electrons appear at any intensity, the result classical wave theory could not explain. Raising the intensity adds electrons but never speeds them up; raising the frequency does. The primary scene is the physical phototube; the side panels are the current-voltage curve (cut off at the stopping voltage, saturating with intensity) and the Einstein line $V_{\\mathrm{stop}}(\nu)$ of universal slope $h/e$.