DECAY OF PHOSPHORESCENCE IN SIDOT BLENDE. 



55 



Table 15. [Dec. 13.] 



Time in seconds required for the phosphorescence to fall to the intensity /. The 

 computed values of t are derived by substitution in the following equations: 



For\ = o.483M 1 /V/ =0. 104+0.070/ 

 X = 0.5 12m i Hi =0.094+0.046/ 

 X = o.547m 1 /Vi" =0. 1 18+0.070/ 



The data of the preceding tables have been used to test the applicability 

 of each of the several proposed laws of decay to the case of a single band. 

 It was found that the results can be closely represented by an expression 

 of the form given in eq. (4). To determine the constants a and b of this 

 equation a convenient graphical method was employed, in which the values 

 of // V7 were plotted as ordinates and times as abcissse. vSince eq. (4) may 

 be written in the form 



the points located in this manner should lie on a straight line. A straight 

 line -having been drawn as nearly as possible through all the points, the 

 slant of this line and its y intercept at once gave the values of b and a respec- 

 tively. The values of a and /; determined in this way are given in each'of 

 the tables, and the values of / computed from the above equation are 

 tabulated for comparison with the times observed. 



Fig- 44- 



Curves .4, B, and C show the decay in 

 the phosphorescence of Sidot blende 

 for the wave-length 0.483 /u, 0.512 p, 

 and 0.547 ix, respectively. The curves 

 A', B' , and C are obtained from A. 

 B. and C by plotting Z~ J - instead of 

 the intensity of phosphorescence, /. 



3 4 



Seconds 



In Figs. 44 and 45 the values of / * have been plotted as described 

 above. It will be noticed that in each case the points lie very nearly upon 



