VALUES FOR FIRST MODE FOR BILINEAR M CURVE 169 
DIN 
FINS 
Mara eerie | 
“NS 
p_ SLOPE OF LOWER SEGMENT OF M CURVE 
Fede SLOPE OF UPPER SEGMENT OF M CURVE 
g=(k2q) "ha 
FicureE 3. Attenuation constant versus anomaly height for bilinear M curve, first mode. 
to the left of the line at —B. Below the barrier U 
shows oscillatory behavior, but with no nodes for 
the first mode; above the barrier U is a spiral, which 
shows only as a slow. increase in the plot of | U |. 
This same difference in the behavior of U for Y >- 
SLOPE OF LOWER SEGMENT OF M CURVE | 
SLOPE OF UPPER SEGMENT OF M CURVE 
O CHARACTERISTIC VALUE FOR G-»00 
% 1.5 (=VALUE OF g ) 
or < —B is a useful thing to remember in more 
general cases. Sometimes it is not quite so clear-cut 
as in this case of trapping. If A is not small, the 
situation cannot be so completely defined in terms 
of B alone. It is certain, however, that | U| will 
Figure 4. Characteristic values for the first mode. 
