平行反射率理论及其实用

用矿相显微镜观察时,在单偏光镜下矿物反射光强与入射光强之比为“反射率”,用R表示。对于处于任意位的非均质矿物,则用Rψ示。在正交偏光镜下,相应光强之比为“正交反射率”,用R+表示。分析镜已推入,但它的方向与起偏镜（前偏光镜）严格平行时,相应的光强之比为“平行反射率”,用符号R∥表示。早在卅年代,贝瑞克（M.Berek）就已提出平行反射率的概念,并推导出了它与物台旋转角ψ及矿物折射率N、吸收系数K关系的公式。

THEORY OF REFLECTIVITY BETWEEN PARALLEL POLARS AND ITS APPLICATION

This article generalized the theory of reflectivity between parallel polars of aniso-tropic minerals Ran and formulated for the first time the functional relation between R(11) and the properties of anisotropic rotation. By the formula, the reflectivity between parallel polars of a mineral can be calculated after measuring its principal reflectivity R1 and R2 and the apparent rotation angle of anisotropism Ar.The article, then, formulated the functional relations among the three factors: reflectivity of anisotropic mineral at random position Rψ, reflectivity between parallel polars Ran and reflectivity between crossed polars R+. In the last part of the article, the relative errors between R(11) and R( )45 of the mineral at inexact position of 45° are calculated.