Measurement of the Refractive Index Using a Modified Constant Deviation Method.

Goniometric methods for measurement of the refractive index of optically transparent materials are considered. A modified constant deviation method is proposed for measurement of the refractive index of a trihedral prism. The proposed modified method does not require measurement of the refractive angle of the prism, which simplifies the measurement process compared to the widely used methods of minimum deviation (the Fraunhofer method) and autocollimation (the Littrow–Abbe method). To implement the method, a goniometric system was used, designed to measure angles formed by flat surfaces of objects. In order to obtain a reflection of the refracted ray, a fixed mirror was placed in its path, and the refractive index of the prism material was calculated from the solution of a system of equations. Results are presented for an experimental study of a triangular prism made of optical glass using the proposed method, and they are compared with results obtained using the method of minimum deviation. The proposed method of constant deviation can be used to study trihedral prisms made of optically transparent materials, as well as liquid optically transparent substances placed in a hollow trihedral prism. [ABSTRACT FROM AUTHOR]