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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 260

An illustration from Light, photometry and illumination : a thoroughly rev. ed. of ''Electrical illuminating engineering'', 1912, leaf 260 — , and F = 47:r^E. .■.E = ^*=^ (165) Therefore the illumination produced by a sphere of uniform bright-ness is inversely proportional to the square of the distance fromthe center for all distances from the surface of the sphere toinfinity. ILLUMINATION CALCULATIONS 245 A Hollow Spherical… … Fig. 145.—A hollow spherical source. When OP is reduced to zero the illumination due to the disk isTzh, and hence the illumination at 0 on an elementary plane areain the diametral plane is tz times the brightness h of the surfaceof the sphere. We have already seen that the total flux froma unit of…

Light · Photometry · Electric lighting

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