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 237
distances. 222 LIGHT, PHOTOMETRY AND ILLUMINATION and the unit of illumination is taken as the surface brilliancy ofthe source, then the percentage value of the illumination on theinterior of the sphere is equal to 100, divided by the square of thediagonal AD. For convenience any sphere passing… … 10 11 12 13 14 16 Fig. 126.—Equilux spheres. and to ascertain immediately for any desired point within thespace explored the exact value of that component of the lightflux which is normal to the particular equilux sphere passingthrough that point. In Fig. 126 are indicated numerous equilux spheres…
Light · Photometry · Electric lighting
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