photoelectromagnetic effect, the formation of an electric field in an illuminated semiconductor placed in a magnetic field. The electric field is perpendicular to the magnetic field and to the flow of the current carriers (conduction electrons and holes), which diffuse through the semiconductor away from its illuminated side, where the absorbed photons produce electron-hole pairs, toward the dark side. This effect is observed when there is a sharp nonuniform concentration of the minority carriers, which occurs with intense absorption of light. Discovered in 1933 by I. K. Kikoin and M. M. Noskov, it is used in semiconductor studies.