248 



TABLE 276. 

 BLACK-BODY SPECTRUM INTENSITIES (J\). 



Values of J\ using for Ci, 0.23 X io, Ct, 14350., X in M- W the figures given for J\ are plotted in cms as ordi- 

 nates to a scale of abscissae of i cm to i M. then the area in cm' between the smooth curve through the resulting points 

 and the axis of abscissae is equivalent to the radiation in calories per sec. from i cm* of a black body at the correspond- 

 ing temperature, radiating to absolute zero. The intensities when radiating to a body at a lower temperature may be 

 obtained by subtracting the intensities corresponding to the lower temperature from those of the higher. Ihe nature 

 of the black-body formula is such that when \7' is small, a small change in Ct produces a great change in /A; e.g., 

 when Ci/Xr is 100 or 10, the change is 100 and 10 fold respectively; as Xr increases, the change becomes proportional; 

 e.g., when Ct/ Xr is less than 0.05, the change in /* is proportional to the change in 62. 



See Forsythe, J. Opt. Soc., 4,331, 1920, relative values, 0.4 to 0.76 ju. (steps o.oi /.), 12 temperatures, 1000 to 5000 K. 

 SMITHSONIAN TABLES. 



