APPENDIX. 333 



M, A, B, C, D> E being certain arbitrary coefficients. By the 

 reasoning of the text it appears that fa = and that c/> 3 may be 

 neglected. The above value of < 2 agrees with Green's result. 



Note to p. 269. 



The intensity of the reflected light attains a minimum value 

 accurately when 



a 



which, by (27), gives 

 b 



02 



and, for the minimum value of , 



a 



{V + (ft - l)'}i (4 + (ft - l)f - fri," + I) 2 



(5^ - 8/t 1 + 1)* ^ - V + 5)* - Qi" + 1)' 

 (5/i 4 - 2/* 2 + I)* (jj, 1 - 2/t 2 + 5)* + (^ + 1)' ' 



If /^. = - , as when the two media are air and water, we 



O 



If /^ = - , as when the two . media are air and glass, we 

 get | = ^ nearly. 



,02 



And the minimum value of ~ can never be greater, even 



/5+l v 2 



Again, 



1 1 



, _ , 

 tan ( 6l + e) = ^j-p - 



"" 



