388 Mr Bevan, The Influence on Light reflected from and 



And again with v = v x — iv 2 , a being = a + ib, this ratio 



net — v 1 + i (nb + v 2 ) 

 na + Vj + i (nb — v 2 ) ' 



so that in this case the change of phase on reflection is 



p n 2 (a 2 + b 2 ) - v? - v£ ' 



And for the additional change of phase due to the current 



<& = ^— oi\ + — bv 2 , 

 ov 1 ov 2 



where Bv lt Bv 2 as before, are equal to 



9 



Vi + v 2 v-c + v 2 



We get the change of phase in this case as a fraction of the 

 wave-length 



\ P tan ^ . t 1 - 3k 2 



4ttV n' 3 (l + k 2 ) 3 ' 



for incidences not very far removed from the normal, so that again 

 the change is too small to be measured. 



Consider now the effect of the current on the velocity of the 

 light transmitted through the metal. In the metal the velocity 

 of the light is 



V'=—P 



\^l 2 + v 1 2 _' 



V 

 and this = , 



Va/ 2 + v 2 2 ' 



The velocity V will therefore be different when the current 

 flows in the metal from its value in the metal without any current. 

 The change in the velocity is 



dV\ 



-K— OV. 2 , 

 OV 2 



and is therefore 



pv 2 Bv 2 

 (af 2 + vW 



whicn is ~ / a r^w/ 2 , ~i\ • 



(a/ 2 + v 2 2 f (v x 2 + v 2 2 ) 



Let us now consider the case of light passing through a thin 

 metal plate, and then find the effect on the emergent light of 



