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BELL SYSTEM TECHNICAL JOURNAL 



match is good. It uses the elimination of the bending as a test for refractive 

 match. It also demonstrates the existence of two velocities in quartz, for 

 two images are seen where a glass prism would cause but one. Also by 

 viewing through an analyzer we see that the two images are caused by plane 

 polarized light, the polarization planes being mutually perpendicular. 



If the fluid has an index lower than that of the prism the rays will bend 

 towards the base of the prism. For this reason, light that reaches the eye e 

 from s must travel by the path s qopoe for the ordinary ray, .y qiptC for the 



Fig. 2.38 — Conoscope view normal to the optic axis 



extraordinary ray. Hence the slit as seen through the prism will appear at 

 So for the ordinary ray, at Sf for the extraordinary while the slit as seen 

 directly alongside the prism will appear at .y. If the fluid index matches 

 the quartz prism for the ordinary ray this ray will be unbent at po and qo so 

 that So will appear as a continuation of s. 



If the fluid index is too high the image so will appear to the left of s with 

 Si still to the right of So. 



As the refractive indices of quartz for the ordinary and the extraordinary 

 ray differ by .009 the apparent separation of So and s^ represents .009 and 



