498 



L. P. Wheeler— Dispersion of Metals 



Hence n/c is seen to be of the nature of an extinction or 

 absorption coefficient. 



Now in equation (1) it is to be observed that the values of K 

 and a contemplated are those operative for currents of the 

 frequency of those set up by the incident wave-train. If we 

 use the (constant) values for them given by experiments with 



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steady currents, the equation yields, on equating the imaginary 

 and real terms of each side 



2ttC s 



and ?* 2 (1 - k 2 ) = K , 



relations, which as has been many times pointed out, are far 

 from being experimentally confirmed. And in view of the 

 enormous frequency of the currents which accompany light 

 waves, it is not surprising that such discrepancies should 

 present themselves. If, however, K and a can be expressed as 

 functions of the frequency, then equation (1) will yield disper- 

 sion formulae with which the results of experiment can be 

 compared. Such expressions for K and a have been obtained 



