The Optical Constants of Crystals of Selenium and Tellurium for Wave-Lengths from 3000 to 5000 Angstroms

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Abstract
The measurements were made by a photographic method, for two positions of the crystal, (1) with the optic axis parallel, and (2) with the axis perpendicular to the plane of incidence. Two sets of optical constants were found for each substance. For selenium, in the parallel position the index of refraction was found to vary from 3.4 to 4.4, and the reflecting power from 0.38 to 0.46; in the perpendicular position the index varies from 2.3 to 3.1, and the reflecting power from 0.41 to 0.34. For tellurium, in the parallel position the index varies from 1.9 to 2.9, and the reflecting power from 0.10 to 0.27; in the perpendicular position the index varies from 1.7 to 2.7, the reflecting power from 0.09 to 0.23. The average error is estimated to be about 5 per cent. The accuracy is greatest for the middle range of wavelengths, 3500-4000 A.