( 325 ) 
. (6) 
The quantity 0.), which we shall have to determine further on, may 
properly be called the complex index of refraction, and if 
a will be the real index of refraction, and h the index of absorption, 
the amplitude diminishing in the ratio of 1 to <H“ when a distance 
l is travelled over. 
From (5) we infer 
S?x = — il*) £y 008 
= G*) («,»•»- «*•»). 
= (»*>«,«»»< 
and then from (4) 
2>* = (p)’ (g» ms & — (?, sin i>) cos f>, 
£>, = (,iy £> 
_(p)« (8* 
If here we substitute the values (3), and if we put 
l + .W 
fJl-M, J = 5 ,.(10) 
O, O, 
we get the relations 
e I + ig«y = (i + D(e*«»»- e=sin»)«>s», 
<z y - *se* = ( i + S)«j. 
(i + ij> g„ = - (i +§)(«*«»» —*»<“»)«»»#. 
Before proceeding further it wiU be well to turn the axes of x and 
2 in their plane over an angle ft, so that the second of them takes 
the direction of the rays. Calling the new coordinates x' and s', 
we have , 
= €* cw €* = — 
by which our last three equations become 
<£V sin # + i £ <£ y = § cos 
— i g (€*«» # + #) = § €* 
(1 + ij) # = fa -7 D ^ 
Finally, if the value of drawn from the third equation is 
substituted in the first and the second, we get the following relations 
between the transverse components of the electric force 
