A numerical examination of the optical properties of thin metallic plates

The optical properties of thin metallic plates have been investigated by a number of physicists. One of the earliest workers in this field was MacCullagh. He predicted from theory and verified by experiment that if light incident on a gold leaf were plane polarised the transmitted beam would be elliptically polarised. With the improvement in experimental methods since MacCullagh’s day, and the gradual removal of obscurities from the theory of metallic reflection and transmission, we now expect much more than a mere general agreement between theory and experiment. We look for an almost exactnumerical coincidence. The condition of the reflected or transmitted beam is precisely described by means of two quantities—the ellipticity and the difference of phase between the components of the light polarised perpendicular and parallel to the plane of incidence. The object of the present paper is to obtain convenient formulæ for these quantities and to compare them with the results of experiments, selecting the most careful and the most recent that are available. We shall admit into our theory no principle that has not found general acceptance, and shall thus be enabled to decide whether such principles are sufficient to colligate all the facts. If they fail in this, it will behove us to look for new principles, or, by a scrutiny of our so-called “facts,” to indicate in what way experimental errors have brought about an apparent conflict between fact and theory.