Equation relating the kinetic energy of an electron, emitted from a conductor illuminated by monochromatic photons, and the photon energy and work function of the surface from which the photoelectron is emitted. \(½m_{\rm{e}} \nu_{\rm{max}}^{2} = h\nu - \phi_{0}\), where \(m_{\rm{e}}\) is the mass of an electron, \(\nu_{\rm{max}}\) the maximum velocity of the emitted electron, \(h\) the Planck constant, \(\nu\) the frequency of the illuminating photons, and \(\phi_{0}\) the photoelectric work function of the surface.