248 



Table 278. 

 BLACK-BODY SPECTRUM INTENSITIES f/X). 



Values of J\ using for C\. 9.23 X lo^, Cj, 14350., X in /x. If the figures given for J\ are plotted in cms as ordi- 

 nates to a scale of abscissae of i cm to i ju, 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 p>er 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. The nature 

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

 when Cj/Xr is loo or 10, the change is loo and 10 fold respectively; as XT increases, the change becomes proportional; 

 e.g., when Ct/ XT is less than 0.05, the change in J\ is proportional to the change in d. 



See Forsyihe, J. Opt. Soc, 4,3.31, 1920. relative values, 04 to 0,76 (i (steps q.qi fi), w temperatures, 1000 to 5000° K. 

 Smithsonian Tables* 



