Light visible and invisible : a series of lectures delivered at the Royal Institution of Great Britain, at Christmas, 1896 (1897)
Thompson, Silvanus Phillips, 1851-1916, Royal Institution of Great Britain · New York : Macmillan · leaf 140
ontal,—then we have the bright field of trans-mitted light. When the planes of polariser and analyser Ill POLARISATION OF LIGHT 119 are crossed—one vertical, the other horizontal—thenthe light is cut off, and we have the dark field. There is a gem called the tourmaline which, whencut into thin… … Fig. 75. Fig. 76. there is now introduced a thin slice of brown tourmaline(Fig. 77). It looks dark, for it cuts off more than halfthe light. But such light as succeeds in getting throughis polarised—the vibrations being parallel to the longerdimension of the slice. A second thin slice of…
Light · X-rays
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