014 Table 309 



BLACK-BODY SPECTRUM INTENSITIES (J\), 50° TO 20000°K. 



Values of J\ using for Ci, 9.23 X io 3 , d, 14350., X in /x. If the figures given for J\ are plotted in cms as ordi- 

 nates to a scale of abscissae of 1 cm to 1 n, then the area in cm 2 between the smooth curve through the resulting points 

 and the axis of abscissae is equivalent to the radiation in calories per sec. from 1 cm 2 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. The nature 

 of the black-body formula is such that when X7" is small, a small change in C2 produces a great change in J\; e.g., 

 when d/\T is 100 or 10, the change is 100 and 10 fold respectively; as \T increases, the change becomes proportional; 

 e.g., when C2/ \T is less than 0.05, the change in J\ is proportional to the change in C2. 



See Forsythe, J. Opt. Soc, 4,331, 1920, relative values, 0.4 to 0.76 it. (steps 0.01 /x), 12 temperatures, 1000 to 5000 K. 

 Smithsonian Tables. 



