Abstract
It is sometimes impossible to make measurements of the refractive index of a solid using an Abbe refractometer. Under these circumstances simple and accurate measurements can be made by immersing the solid in a liquid whose refractive index can be varied until it matches that of the solid. This paper describes methods which ensure that the match is made to a high degree of accuracy. Multiple beam interference fringes are sensitive to small changes in refractive index and examination of Fizeau fringes formed by light passing through the solid and through the liquid only, reveals such small changes. Heating or cooling of the liquid then enables the match to be made exactly. By determining the dispersion of the immersion fluid, fringes of equal chromatic order provide a simple and quick method for obtaining the dispersion of a solid.
Published Version
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