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 156
Numerous other contrivances are used for a similar purpose.A single mirror may be used with an arrangement of apparatusas indicated in Fig. 80.^ In this case the lamp is moved aroundthe mirror and the mirror turned with the lamp so that the raysfrom different directions around the lamp will strike… … Fig. 79.—Mirror for determining the distribution of light. notice. It will be seen that the direct rays from the lamp areintercepted by a black screen placed in the photometric axis.The light which is measured is reflected by the mirrors andstrikes the photometer screen at an acute angle. This…
Light · Photometry · Electric lighting
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