Principles and practice of electrical engineering (1914)
Gray, Alexander, 1882-1921 · New York [etc.] McGraw-Hill Book Company, inc. · leaf 389
not clearly seen. 398. Intensity of Illumination.—The unit of light intensityis that produced by a source of one candle-power at a distance of1 ft. and is called the foot-candle. In Fig. 432, the same amount of light strikes the surfacesA, B and C, so that the intensity at B is less than that at A… … Fig. 432.—Variations of light intensity with the distance from the source,and with the angle of incidence. Curve D, Fig. 432, shows the light distribution curve of a 40-candle-power tungsten lamp equipped with a reflector for street lighting. It is re-quired to determine the illumination at a point…
Electrical engineering
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