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 104
and partlyby the other. In the equality of brightness photometer the rays from I^ passdirectly through the central part of the prisms illuminating the THE PRINCIPLES OF PHOTOMETRY 89 central portion of the field as indicated in Fig. 32. The raysfrom I^ pass in the same way into the prism B, the… … Fig. 33.—The Lummer-Brodhun contrast pliotometer. are indicated by the full lines. Those shown dotted from I^ arereflected by the prism B out of the line of vision while thoserepresented by the dotted line from I^ pass directly through theprisms out of view. With this arrangement one observes a…
Light · Photometry · Electric lighting
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