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 123
his voltage. The galvanometer is shownagainst the wall and the translucent scale, on which a spot oflight is thrown by the mirror of the galvanometer, may be seenjust back of the potentiometer. A rotating sectored disk maybe seen in the photometric axis to the left of the photometerscreen. A series… … THE PRINCIPLES OF PHOTOMETRY 109 between the two lamps have openings at their centers and theyare so placed that the direct rays from the lamps reach thephotometer screen unobstructed. These screens may be madeof black velvet or of any material and painted a dull black.Unless the material of which…
Light · Photometry · Electric lighting
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