16 Mr. A. A. Michelson on the Application of 



Finally, when — =1, 3, 5, . . . 2m— 1. 



tan 



ira 



7 o 5 2m— 1 

 an^— = +go, tan — -=oo, and — = ~, ^ . . . — ~ — , 



2a — a u Z Z A 



iry 



and when — =2, 4, 6, . . . 2m, 



7T7 



7_ 



tan—- =0, tan -'- = 0, and -*- =1, 2, 3, ... m. 



2ct « «o 



The curve obtained is shown in fig. 9. 



Fig. 9. 



3- C « * » ^V;f r = ^ fsr./% 



^ciSSouC • 



2nd. When the opening observed is circular, the expression 

 for the intensity becomes 



I 



EV5P 



P 



sin 2 - (7-^)) 



d<f>. 



(24) 



