PHOTOGRAPHIC STUDIES OF LUMINESCENCE. 



127 



I 



50 



40 

 30 

 20 

 10 



slit opened 40 units. Curves 1,2,3, and 4 represent the spectra of acetylene 

 light at intensities 32, 16, 8, and 4 respectively. Curve 7 represents the 

 spectrum of the fluorescence light. Curve 6 represents the distribution 

 of energy in the acetylene flame and is assumed to correspond to curve 3. 

 Then the energy curve corresponding to curve 2 will have ordinates equal 

 to 16/8 times the corresponding ordinates of curve 6, etc. Wherever curve 

 7 crosses curve 3, the energy for that wave-length is represented by the 

 ordinate on curve 6 for that wave-length. Wherever curve 7 crosses curve 

 2, the energy for that wave-length is 16/8 times the ordinate of curve 6 for 

 that wave-length, etc. 



Since the curves intersect at only a fewpoints.it was necessary to get other 

 points on the desired energy curve by interpolation. This was done sys- 

 tematically and as follows: Suppose wave-length m is under consideration. 

 A curve is plotted with the intensities of acetylene, 4, 8, 16, and 32, as 

 abscissas and the intersections of the vertical at /n with the curves 1, 2, 3, 



4 8 



16 

 Fig- 134- 



32 



and 4 as ordinates. From this curve is picked off the intensity of acety- 

 lene that would have coincided with curve 7 at wave-length ;ui. Fig. 134 

 shows six curves drawn in connection with Fig. 133. Curves 1, 2, 3, 4, 5, 

 and 6 correspond to wave-lengths ,0 = 0.50, 0.51, 0.52, 0.53, 0.54, and 0.55 

 respectively. The circle on each curve shows the point picked off. On 

 curve 6, Fig. 134, 23.5 is the abscissa corresponding to 2.8, the ordinate on 

 curve 7, Fig. 133, at ^ = 0.55. Hence the ordinate at ju =0.55 on curve 5, 

 133, which shows the distribution of energy of the fluorescence light is 



Fig. 



equal to 



23-5 



times 21.3, the ordinate on curve 6, Fig. 133, at ^ = 0.55. 



Curve 5, Fig. 133, shows the energy curve of fluorescence as computed 

 from the other curves in Fig. 133. The curve has a well-defined maximum 

 at ^ = 0.55 and a minimum at /i = o.6o. The shape of the curve for wave- 

 lengths greater than yu = o.6o is uncertain. 



Fig. 135 shows another set of curves corresponding to those in Fig. 133. 

 The length of exposure was 30 minutes for each spectrum with a slit width 



