Extraordinary ray (e). 25 °C.
1) T. M. Bieniewski and S. J. Czyzak. Refractive indexes of single hexagonal ZnS and CdS crystals, J. Opt. Soc. Am. 53, 496-497 (1963)
2) M. Sanchez Gomez, J. M. Guerra, and F. Vilches. Weighted nonlinear regression analysis of a Sellmeier expansion: comparison of several nonlinear fits of CdS dispersion, Appl. Opt. 24, 1147-1150 (1985)* Ref. 2 provides Sellmeier equation based on the data from ref. 1