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BELL SYSTEM TECHNICAL JOURNAL 



Figure 3.2 gives information concerning the phase velocity of the wave 

 in the form of a plot of (/So/t) cot i/' as a function of /3o a cot yp. 



The ratio of the phase velocity v to the velocity of light c may be expressed 



v/c = /3n//3 = (y/(3)i^o/y) cot i^ tan rp 

 v/c = (7//3) tan i/- [(/^o/t) cot ^ ] 



(3.4) 



f^oa COT x/j 



Fig. 3.3 — From these curves one can ol)tain v/c, the ratio of the phase velocity of the 

 wave to the velocity of light, for various values of tan \p and /3oa cot \^. 



From Fig. 3.2 we see that, for large values of (ioa cot \J/, (i^o/t) cot \}/ ap- 

 proaches unity. For slow waves y/0 approaches unity. Under these circum- 

 stances, very nearly 



v/c = tan \f/ 



i^.S) 



If the wave traveled in the direction of conduction with the speed of hglil 

 we would have 



v/c = sin yp 



