On the mixing of photoelastic immersion fluids

It is shown that an equation can be used to determine the exact quantities of components to yield a specified refractive index for an immersion fluid. The results obtained from this equation are compared with values obtained experimentally for two different immersion fluids, IMF 163 and Hallowax. The paper also discusses the kinds of errors that are introduced when a mismatch in refractive index occurs between model material and immersion fluid. Graphs are presented which show the effect of temperature on the refractive index, the degree of refraction of the light beam when the refractive indices are different between immersion fluid and birefringent model, and effect of the angle of incidence.