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 167
intensityin terms of a linear quantity. Moreover, only an angle protractorand a pair of compasses are necessary for its construction. Thismethod consists in determining graphically an evolute from thepolar curve of the luminous source, together with its involuteand then projecting this involute… … Fig. 88.—Device for obtaining mean hemi-spherical candle-power. to zones of 15 degrees. Find the radii of the midzones, repre-sented by the dotted lines, oz, on, ov, ow, ox, oy, respectively.Then with o as a center and with a radius oz describe the arc izthrough an angle of 15 degrees. Draw the…
Light · Photometry · Electric lighting
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