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 256
ions.—2-^1.3 = 1.54 foot-candles required of one tube. The first trial spacing will be 15 ft. Height of tubes abovereference plane = 15/1.5 = 10 ft. Under the center of the tube Let L = 30, A = 10, then w = 0.33 and at p = 0.5, /v=2.88/ 2^8 /X With this spacing the necessary candle-power per foot… … Fig. 141.—Illumination contours. the spacing will be increased to 18 ft. This value will leave only3.5 ft. between the side tubes and the wall, and will undoubtedlyprove more effective. Leaving the length unchanged, L = 30 ft., / 2 77 / h = 12 ft., 7w = 0.4, and at p = 0.5, A = 2.77, 1-54 = ^…
Light · Photometry · Electric lighting
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