Lockyer, Norman, Sir, 1836-1920, Seabroke, G. M. (George Mitchell), 1848-1918 · London, Macmillan and co. · leaf 470
nd o as they revolve round the CHAP. XXX.] THE TELEPOLARISCOPE. 447 centre s of the screen, the images produced by theordinary and the extraordinary ray becoming alternatelybright and dark as the crystal is rotated. Fig. 206shows the images on the screen when the ordinary rayis stopped by the first… … Fig. 206.—Appearance of Spots of Light on Screen on rotating the second Crystal,when the extraordinary ray is allowed to pass through the first Screen. There is an objection to the use of it, as it is not verytransparent, and a Nicols prism is now generally usedfor polarizing light. It is…
Astronomy · Telescopes
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