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



or, finally, 



Sill 7T- 



v= 



(4) 



a 



Hence the fringes will disappear whenever a is a multiple 

 of «o« They will be clearest when 



a a 



01= — tan ir — 



(5) 



7T a 



The curve of visibility will be of the form given in fig. 2. 



Fig. 2. 



The successive values of the maxima, disregarding signs, 

 calculated from the above equation, are : — 



V = + 1-000 



V = - 0-210 



V = + 0-130 



V = - 0-091 



The negative values mean that during the corresponding 

 period the fringes are reversed*. 



As the expression for V contains X, the wave-length of 

 the light employed, the fringes can disappear for that colour 

 (and the complementary one) only; and as this will be most 

 decided for the brightest colour in the spectrum, the yellow 

 or greenish yellow (and therefore also for violet), there will 

 be a residue of red and blue-green mixed with much white 

 light. Both of these deductions have been fully verified by 

 experiment. 



/L-I 2 \ 2 



* Probably the expression for V should be u' / I ,but this will not 



affect the position of the points for which V=0. 



