183 
23 IV. EFFECTS OF PRESSURE WAVES 
4.  IMMOVABLE INTERFACE 
Figure 10 
for 6 =0, in a double plot whose mode of construction is sufficiently obvious. Val- 
ues for three target materials in contact with sea water, for 6 =0, are as follows: 
-0.99946 
0.00054 
1 - 0.00109 
IV. EFFECTS OF PRESSURE WAVES 
5. STEEP-FRONTED WAVES 
5. STEEP-FRONTED WAVES 
If the incident wave has an extremely steep front, as has the pressure wave 
in water resulting from a detonating explosive, the wave transmitted into the target 
will also have a steep front. Waves of this character are easily produced in solid 
material by impact, and there is no evidence that they possess any special tendency 
to rupture or distort the material. It may be concluded that the precise shape of 
the steep front of the pressure wave is probably of no practical interest. Nor should 
the effects of the secondary impulses be altered much by the mere fact that they prob- 
ably have no steep fronts at all. 
The general form of the pressure wave may, however, be of importance, in 
some cases because of resonance effects. 
IV, EFFECTS OF PRESSURE WAVES 
6. INTERNAL INTERFACES 
6. TARGET WITH INTERNAL INTERFACES 
The simplest type of a non-homogeneous target is one in which internal in- 
terfaces occur, as at the inner surface of a ship's plating. Additional reflections 
