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 243
n connection with the law of conservation relative to theproduction and utilization of flux, the apparent inaccuracies inthe simplified proofs of the uniformity of illumination disappear.Illumination on Horizontal Planes.—(McAllister, Ref. Cit.)In the solution of the practical problems given above… … Fig. 13.3.—Proof of equality of equilux sphere and floor illuminations. such an assumption involves the conception of definite directionof flux coming from an extended surface source it is open to theobjection noted above under uniformity. However, in sofar as any direction can be assigned to the…
Light · Photometry · Electric lighting
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