then 



REFRACTED AND REFLECTED LONGITUDINAL WAVES 



{Pm Pm) — ~ (°m "mjrel 



Qm l^m, p + Qm + 1 ^m + 1, p 



and if Vp<^m-i, p' then 



/p' p' \ _ IP' P' \ , Q'n'^m,P Q m-l'^m-1, p . 

 ^m ^'m, p T^ Qm-1 '^m-l, p 



23 



Fig. 6. Curves for calculating the coefficient of reflection of longitudinal waves 



from the layer boundary- with a lower velocity of propagation than in the layer in 



which the incident ray is travelling. 



Case c. The value of the coefficient of reflection (Pq'^o') is taken at the 

 point X = sin ao along the ordinate from the curve (see Fig. 7) corresponding 



