Laurence, Lionel · London, School of Optics · leaf 291
llel to the axis. Iceland Spar.—Spar or calcite, like quartz and tourmaline, has the powerof double refraction, but since the ordinary wave has a higher index thanthe extraordinary, it is termed a negative crystal. The index of the ordinaryray is 1-659 and that of the extraordinary 1486, so that…
Optics
Internet Archive · Gerstein Library, University of Toronto · Public Domain Mark 1.0. Free to use for anything.
