Studies in refractive index III

Abstract

In this paper experiments are described which indicate by direct interferometric measurements the distance of penetration of light into the second medium at total reflection. The intensity of the superficial wave is greater in the case when the electric vector of the incident light is in the plane of incidence than when it is perpendicular to this plane, as is required by theory. A method of multiple reflection was devised whereby the reflection coefficients in the two cases could be photometrically compared when the second medium is absorbing. The absorption coefficient and the refractive index of the liquid were measured in layers of the order of 10−3 cm thick and the values compared with the values deduced from the theoretical equations for the reflection coefficients. The results indicate that, for a saturated aqueous solution of potassium permanganate, the solvent is preferentially adsorbed at the surface, giving rise to smaller absorption of the superficial wave than would be expected from measurements of the absorption coefficient in the bulk.