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 91
ature and itsreliability is of great importance. Having a reliable lightstandard the next important feature is the photometer. Aphotometer is an apparatus for comparing illumination intensities. All elementary photometry is based on the assumption of apoint source of light and that the intensity of… … 12 3 Fig. 23.—Law of inverse squares. methods of photometry are elements of common knowledge, abrief review at this time, may not be out of place. A graphicalpresentation of this law is shown in Fig. 23, where the source oflight is assumed to be at 0 and the rays emitted radially in alldirections.…
Light · Photometry · Electric lighting
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