XIX. New contributions to interferometry. Part III.—The differential polarization phase change on reflection at a thin silver film

Summary The differential phase change at reflection, for light polarized in and perpendicular to the incident plane, is determined for a silver film. Green mercury light is used, the film being one-tenth of a wave thick. The differential effect is measured interferometrically by a multiple beam Newton's ring apparatus described elsewhere. The effect is measured over an incidence range of 0° to 80°. To the first order the experimental results confirm the predictions of classical electromagnetic theory. Up to an incidence of 60° the experimental curve of the variation with incidence is parallel to the theoretical curve but slightly displaced upwards (by 0·007 λ). There exists a marked point of inflection at 63° which is not predicted by theory. The existing theoretical treatment is considered to be incomplete.