wherein the noted terms can be neglected: 
u 
a 
2 
, 
A a eT - = =o (25) 
Making the same neglection as for deriving (25), it is found 
from (21a) 
@'-£@ x 
These two equations (25) and (26) correspond to (20) and 
4 
(21) and combining them, the following equation for @ as func- 
tion of @ is found: 
= () 
@ -@O@ +247 -0o (27) 
which has only real solutions as long as 
2 
+ 
- 247 20 
Therefore the assumption for these calculations, that is the 
incident and the reflected shockwave, is only correct for Os @ 
AT 
with 
= . Tr 
2 ea (28) 
Combining (28) with the formula (14a) for the critical 
angle at a free surface reflection, it will be found 
@. =aic (29) 
A Crié 
31 
1459 
