( 68 ) 
We saw already that the place of the absorption-lines is deter- 
mined by the conditions 
S} Ee 0 and Sy zn 0 ’ 
i. e. by 
We have further assumed that &R.% is much larger than & 4 
Hence, in the equation (24), the coefficient of U is approximately 
+ RG, so that 
TEE Vo OS ee ae 
On the other hand, we may neglect in (25) the last term, at 
least if & has a value for which the absorption is a maximum. 
For, neglecting #°, we find for that term 
1— 27% 
(w@* — v?) + 2 v*z 
ee AACS be, ag weet a ane 
The equations (22) and (23) show that, in the middle of one of 
the absorption-bands, @?—v? is much smaller than 2v’z. We may 
therefore neglect the first term in the denominator. Omitting like- 
wise in the numerator the second term, which by our assumption, 
lies far beneath 1, we find for (27) 
gq? Po? v? Vr Sabine J? Vv, 
Derk 2x 
But, according to (23), the maximal absorption is given by 
(27) may therefore be finally replaced by 
EA 
a qaantity that may be omitted in (25) as well as #0 & V in the 
first term of that equation. In this way (25) reduces to 
Vs Us 
which agrees with (26). 
Tanelaied into the terms of the electromagnetic theory of light, 
our result becomes 
