ABSTRACT
This chapter explores the several methods of measuring refractive index of a liquid and a solid substance. These can be grouped into two: methods using spectrometer or a goniometer and methods based on the measurement of critical angle. Abbe refractometer is the most commonly used instrument for the determination of refractive indices of liquids and solids. Ellipsometry is used to measure thicknesses of thin films on dielectric or metallic substrates. It is also used for determining the refractive index of a transparent film and to obtain the complex refractive index of the substrate. Physical and chemical absorption, oxidation, and corrosion modify the state of polarization of the incident light and hence have been studied using ellipsometry. Interferometry responds to optical path difference, which is a function of geometrical path, refractive index, and wavelength. Interferometry is a highly sensitive technique to detect and measure the refractive indices.
