This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1912 Excerpt: ...We have in which K represents now the diffuse reflection coefficient. The area S is a second radiator with the flux K£. 72. REFLECTION IN A SPHERE.--Consider the simplest case, a white diffusing hollow sphere with a radiating surface A S, for which the polar curve (1) is a circle (see fig. 4''15). The impinging ray I has the intensity I" cos 6, and as the angle of incidence on A Sj is 6, we obtain for the illumination of A Sj the value Epcos. (2R)2'' whence it follows that the sphere is uniformly illuminated. The total flux is therefore given by tf = SE, where S is the area of the sphere. AS A Si Fig. 4"15.--Reflection in a Sphere. So far we have neglected reflection altogether. The flux f which strikes unit area of the sphere is reflected the first time as Kf, and as this applies to all parts of the sphere the illumination is increased uniformly to the extent of. On emerging again the flux is reduced to K2/ so that the second increase in the illumination of the sphere will be This reflec tion goes on indefinitely, causing a total illumination of the sphere 1 _ 1 1-K a'' and E = =£ 4-20 These equations apply of course to spherical chambers only, but they indicate that for all rooms we get considerable assistance from reflection if we employ "surfaces with large reflection coefficients. In the following table, the values of K, a, and--have been plotted. a The next table shows a number of diffuse reflection and absorption coefficients for various colours, as given by Dr L. Bell, in the Convention issue of the American Illuminating Engineering Society. The table holds chiefly for wall-papers illuminated by incandescent lamps. On studying this table we see that the light cream and yellow colours are by far the best, that apparently light ...