erselyproportional to the square of the distance of the point from the The proof may be put rather diffe-rently thus. Let 0 (fig. 9) be a sourceemitting light uniformly in all directions.With 0 as centres describe a series ofspheres of radii 1, 2...r cm. Light isenergy travelling outwards from the… … Fig. 9. 10-12] VISIBLE RADIANT ENERGY — LIGHT. 15 Thus the total quantities of light falling per second on each sphererespectively are 4^^ , 47r2272 , . . . 47rr2Jr , and these are equal, thus But Jj is the illuminating power of the source, Ir the intensity of theillumination at distance r. 11.…
Heat · Light
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