The polarization of light by narrow slits

Abstract

The fraction of the incident light transmitted by various narrow slits of finite depth and with metal walls is measured for two states of polarization and two wave-lengths of the incident light. It is found: (1) that real, narrow slits do not transmit all the incident light; (2) that the transmission losses increase when the depth of the slit is increased, and decrease when the conductivity (or reflectivity) of the slit walls is increased; (3) that when a slit is more than about half a wave-length wide, light polarized with its electric vector parallel to the slit is transmitted better than light polarized with its electric vector perpendicular to the slit, and that for either state of polarization the fraction of incident light transmitted increases as the wave-length is decreased; (4) that a slit less than half a wave-length wide transmits light polarized with its electric vector normal to the slit only, and that in such a slit the fraction of incident light transmitted increases as the wave-length is increased. It is shown that the existence and order of magnitude of all these effects may be predicted from the electromagnetic theory of light, and that some of them may be expected from a consideration of the older scalar wave theory. The paper includes some brief notes on the transmission of light by dielectric slits and on the diffraction patterns produced by slits of finite depth, and concludes with some applications of the observed phenomena.