Illuminating Engineering Society, Association of Public Lighting Engineers (Great Britain) · [London] · leaf 272
regularly as the angle of emission increases.The curve in Fig. 37 is approximatelyan equiangular spiral, and plotting withrectangular co-ordinates as in Fig. 38,the equation to the straight line is93° _ 0-33f, where e is the angle ofemission measured in degrees, or generally, b = 1^ — aewhere b is… … FiG. 36.—Family of curves of reflexion from Bristol board, lHii> THE ILLUMINATING ENGINEEB (seft. 1919) ment shown in Figs. 8 and 12, where three facets, A, B and C (Fig. 39), eachthe range was 40 per cent. If the being matt, not polished. The particlereflecting power had not fallen off, if is…
Lighting
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