Light and lighting . number of zones Fig. 1 the distance Q R is 0-598 ifO G is unity. It is easy to show that ifthe geometrical construction were madewithout error, and QR were scaledcorrectly, the length would be 0-5973 asfar as four significant figures. Comparingthe actually measured length 0*598 withthe theoretically deduced value of 0*5933,given in the Appendix, it will be seen thatin this instance, with only three zones,the result of the graphic construction iscorrect within 1 %. As a general rule,however, 45° zones may introduce anerror of two or three per cent. Theapparent s
Light and lighting . number of zones Fig. 1 the distance Q R is 0-598 ifO G is unity. It is easy to show that ifthe geometrical construction were madewithout error, and QR were scaledcorrectly, the length would be 0-5973 asfar as four significant figures. Comparingthe actually measured length 0*598 withthe theoretically deduced value of 0*5933,given in the Appendix, it will be seen thatin this instance, with only three zones,the result of the graphic construction iscorrect within 1 %. As a general rule,however, 45° zones may introduce anerror of two or three per cent. Theapparent spherical reduction factor =Q R/O h. Moreover, since the total flux of lightemitted by a virtual point source is 4^times its mean spherical intensity, itfollows that if a circle were drawn withradius Q Q, the length of the circum-ference would be equal to the totalluminous flux emitted by the soiree , if the polar intensities arescaled in candle-power, then 2-rr Q Q1, or7-52 x O G will be the total luminous. Fig. 1.—New Diagram of Simple Circular Polar Curve depressed diametrically 45°. Rectified by 45° zones.
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