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Refractive Index of Lead Tungstate Crystal (J21)

The extraordinary index of refraction was measured to be 1.006 and the ordinary index of refraction was measured to be 1.007. This was calculated utilizing the following equation:Θr = γ − (π/2 + α) + sin−1 [ (sin α)(sin γ) + (cos α) q (n^2 – sin^2 γ)]. These values are quite off, possibly because the equation is limited to n<1.225 at a 45 degree angle. This is because sine of any angle will always be less than or equal to one, and in the equation, if the angle of incidence is 45, then the maximum value of n to result in a sine value less than or equal to one would be 1.225. While the angle of incidence could be increased to 89 degrees to maximize the largest possible n value determined, the greatest value of n would still be 1.5.

An alternative method of determining refractive index may be with the following equation: n^2 = 1 + 0.438*rho. That refractive index value will be determined once an appropriate scale has been located. However, that method would only result in one value for index of refraction. This crystal is anisotropic and should have extraordinary and ordinary indices of refraction. It will be interesting to see how the density method might relate to the two indices.