Light, photometry and illumination : a thoroughly rev. ed. of ''Electrical illuminating engineering'' (1912)
Barrows, William Edward, 1878-1960 · New York ; London : McGraw-Hill Book Co. · leaf 142
iiiii iiiiii III 11 Ml nil I III II nil Il i1 Fig. 63.—Ryans photometer. on the test plate F which is observed through the sight tube Vthrough which may also be seen the surface of the plate p, illumi-nated by the comparison lamp B, through a pair of mirrorsSy and S^. These mirrors may be moved… … Fig. 64.—The Burnett photometer. from a scale graduated proportionally to the square of the dis-tance through which the light from B passes in reaching p. In Ryans photometer, Fig. 63, the light to be compared fallsat A upon one surface of the photometric device, 5, whichconsists of a translucent…
Light · Photometry · Electric lighting
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