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 158
the openings in the rotating sector disk and varying the dis-tance between the standard lamp and the sight box. The sightbox should remain in the same position as when the apparatusis calibrated so that the incident angle of the light Ta,ys will be PORTABLE PHOTOMETERS 143 the same. For very low… … Fig. 81.—Arrangement of twin-mirror photometer. ¥— ^ b \ ! \ I i Fig. 82.—Revolvable test-plate for determining the distribution of Hght. Still another arrangement for the same purpose but simplerin construction is illustrated graphically by Fig. 82. Assumethe source to be located at / and a…
Light · Photometry · Electric lighting
Internet Archive · Boston Public Library · Public Domain Mark 1.0. Free to use for anything.
![An illustration from [Electric engineering.] (1902)](https://img.insideoutlibrary.com/img/200/ia-electricengineer03inte-313-191.webp)
