GEOLOGICAL APPLICATION OF SEISMOGRAPHY 1315 
/ N 
/ 
4 
/ 
7, 
/ SOFT 
y LOW SPEEDO 
/ 
/ V, 
Me 
/ 

HARO 
HIGH SPEEO 
C V, 
2 
c 
Fic. 2.—Refraction and reflection of waves in passing from low-speed to high-speed 
medium. 
equals the ratio of velocity in the upper medium to velocity in the lower 
medium. The direction of the reflected ray is such that the angles a and 
b are equal. Refracted and reflected rays must always obey these two 
simple fundamental laws, which may be summarized: 

Snea Vi 
Sine coc V; 
a=b 
where V, is the velocity in the upper medium and V; in the lower. Angle 
a is known as the angle of incidence, angle 6 the angle of reflection, and 
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