Measurement of the refractive index using a modified prism method

Abstract

Goniometric methods of measuring the refractive index of optically transparent materials are considered. A modified method for measuring the refractive index of triangular prisms is proposed. In the previous work [1], a modified constant deviation method was proposed for measuring the refractive index, which does not require measuring the refractive angle of the prism. That modification is simple, but its implementation uses low-intensity radiation reflected from the input face of the prism, which creates difficulties in processing signals from a photoelectric receiver and can lead to an increase in measurement error. In this paper, to obtain the reflection of the refracted beam, we used two fixed mirrors, and the refractive index of the prism material was calculated from the solution of a system of equations. This approach makes it possible not to use radiation reflected from the faces of the prism, which makes it possible to increase accuracy by automating the measurement process. The results of an experimental study of a triangular prism made of optical glass using the proposed modified prism method and their comparison with the method of minimum deviation, which has the highest accuracy of determining the refractive index, are presented. The proposed method can be used to study triangular prisms made of optically transparent materials, as well as optically transparent liquids poured in a hollow triangular prism.