136 



w(n„ — n ) + tng 

 and if we put 



— = « (7; 



we ünd the following values for the case n = «„, i.e. for tlie maxi- 

 mum of absoi-|)tion 



{^i„yz= l—ia, 



2fi/ = Vl + a'+l, 



2— f =1/1 +«'-1. 



"o 



The last equation shows that the smaller the coefficient of resist- 

 ance g, the greater will be the value of /(„ ; small resistances give 

 rise to a strong maximum of absorption. We can in this respect 

 distinguish two extreme cases; viz. that « is much greater and that 

 it is considerably smaller than unity. In the first case we have 

 approximately 



ch„ — 



— = |/i« 



and in the second case 



(3) 



If we write J„ for the wave-length in the aether, corresponding 

 to »o, we have 



cK _ KK 



7i„ ~ 2;t 

 Now, according to (5) the decrease in intensity over a wave-length's 

 distance is given by 



e--^''o'i> (9) 



and we see therefore that this decrease will be considerable if « ^-^ 1 

 and very small if « <^<[ 1. 



^ 3. The width of the bands of absorption may likewise be 

 deduced from equation (6). Indeed, if n is made to differ from ?i, in 

 one direction or the other, the term m{n„' — n') gains in importance 

 in comparison with i n c/ ; when it has reached a value equal to a 

 few times ng, the index of absorption lias become considerably 

 smaller than A„. As the ratio of m(?io' — ?i') to ng is of the same 

 order of magnitude as that of 2?»»„(?? — ?i„) to?i(,^, we may say that for 



