46 
APPENDIX D: 
PERTURBED CYLINDRICAL WAVE FRONT 
The function 
A(r,@) = r+g(g) 
represents the wave front of a radially expanding cylindrical 
wave emitted from the source P(x, yo) after some time ¢ 
(fig. D1). If g(g) = 0, then A(r, g) = r which is a cylindrical 
wave front inthe plane. The quantities r and g are defined 
in the &y coordinate system. 
Y 
A 
SOURCE 
P(x0 , Yo ) 
ELEMENT 
(xc, , y,) 
Figure Dl. Source and perturbed cylindrical wavefront 
passing through a typical element. 
