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 107
e rays illuminating oppositequadrants, as shown in Fig. 38a. This glass absorbs a small 92 LIGHT, PHOTOMETRY AND ILLUMINATION amount of light, the right amount to produce the desired con-trast. The unbahinced condition of the field is shown in Fig. 386.The selenium photometer takes advantage of the…
Light · Photometry · Electric lighting
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