For other uses, see Zechariah. The male given name Zechariah is derived from the Hebrew ×Ö°×Ö·×¨Ö°×Ö¸×, meaning The Lord has remembered.. It has been translated into English in many variant forms and spellings, including Zachariah, Zacharias and Zachary. It was the name of various men in the Bible.
Double Refraction in Minerals Double refraction is the splitting of a single ray of light into two refracted rays when passing through an anisotropic mineral. All anisotropic minerals exhibit double refraction. Double refraction can be practically observed by placing a transparent Calcite (Iceland spar) crystal on a sheet of paper with a black dot on it. When the dot is viewed through the crystal, two dots are seen.
The index of refraction for the ordinary ray is constant and is independent of direction. The index of refraction for the extraordinary ray is a continuous function of direction. The index of refraction for the ordinary ray is independent of direction. The two indices of refraction are equal only in the direction of an optic axis. The measure of birefringence (Î´) [delta] is the difference between the indices of refraction of the two rays.