Finally we introduce the well known relationship between the indexes of 
  
  
  
  
  
  
  
  
2 
here, refraction and density (compare e.g. [3 ). 7-15 cp, where c is a constant, 
for 2 With n = 1 + Q, where à is usually «0.0005, we may write: 
n=} oO D = T ,a-l 
ion "foveas 1 + a s (103) 
O O 0 O 
otted 
+: The 
the 
Ally if 
missile 
of ^h (s 
lly in Du 
pie X (T_) 
. avoids i o p 
h (t) 
he air. : 
d | 
H (T 
refer- A a ( S. 
cated 
follow- 
p s BH (T) 
on and O O 
Figure 14 
or a 
(101) T 1, + | 
- = «A eM € 104 
E cH nn T 3 ( | ) 
ature 
(102) 
65 
a, TT 
UN