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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 144

An illustration from Light, photometry and illumination : a thoroughly rev. ed. of ''Electrical illuminating engineering'', 1912, leaf 144 — m. Eng. Soc, Vol. 2, p. 546, 1907. PORTABLE PHOTOMETERS 129 fore the lens, F. The photometric device, B, consists of crossedprisms through which the ground-ghiss plates, G and G, areviewed, from the binocular arrangement, H. Equality of illu-mination is produced by the adjustment of the diaphragms,… … Fig. 67.—The sector tyije photometer. the test-plate. That which is transmitted passes through the45-degree mirror, E, a convex lens, and falls upon the upperhalf of the translucent screen, B. A comparison lamp, C,illuminates translucent screen, G. Light which is transmittedthrough this screen…

Light · Photometry · Electric lighting

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