This paper describes a simple method of measuring the refractive index of a liquid. The basic element is a thin wedge cell, and the source of light is a low power He-Ne laser. Conditions are derived to obtain the best possible accuracy using this setup. The same setup can also be used for the determination of the refractive index of a solid medium such as glass.
M. V. R. K. Murty,
R. P. Shukia,
"Simple Method For Measuring The Refractive Index Of A Liquid Or Glass Wedge," Optical Engineering 22(2), 222227 (1 April 1983). https://doi.org/10.1117/12.7973088