A dictionary of electrical words, terms and phrases (1898)
Houston, Edwin J. (Edwin James), 1847-1914 · New York, The W. J. Johnston company · leaf 412
ite sides ofsuch a disc is equal, the relative positions of thetransparent and opaque portions of the disc areindistinguishable. Photometer, Varleys A form of photometer in which the intensity of the lightto be measured is determined from the rel-ative openings of two concentric circulardiaphragms… … Fig. 43 T. Varley*s Photometer. cular apertures extend circumferentially 180 de-grees, and are reversed so that when one half ring is fully open, the other is completely closed;or, if one ring, say the outer, is opened 160 de-grees, the inner is opened 20 degrees. Thequantity of light then which…
Electricity · Electrical engineering
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