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 152
ings between the sectors may be seen thescreen D by means of the mirror M. Looking through the eye-piece H the observer sees first theilluminated white surface of a sector of A, and then in themirror M the illuminated surface of the screen D. A photo-metrical balance is obtained by altering the… … Fig. 76.—The Harrison portable flicker photometer. position shown in the diagram the photometer is arranged tomeasure the intensity of illumination normal to a direction of45 degrees to the vertical, but by tilting the photometer theintensity in any desired direction can be measured. By setting the…
Light · Photometry · Electric lighting
Internet Archive · Boston Public Library · Public Domain Mark 1.0. Free to use for anything.
