384 Mr Bevan, The Influence on Light reflected from and 



This equation gives for any direction of wave motion only one 

 velocity, so that in whatever plane the light is polarised the 

 velocity is the same and there is no difference of phase of the 

 components of any vibration introduced on progression through 

 the metal. 



For light incident normally 1 = and the effects on re- 

 flected and transmitted light are the same as when no current 

 flows. 



Consider light, polarised in the plane of incidence, incident 

 on the metal, the forces varying as e L{lx+my+nz+pt) . The values of 

 I, m, n in equation (3) will be I, m and say v. 



The ratio of the amplitude of the reflected light to that of the 

 incident is 



n — v 



n + v 



The metal we suppose thick enough for the first surface only 

 to be taken into account. 



Putting v = v x — lv 2 , 



so that Vj and v 2 are positive, the effect becoming zero for z large 

 and negative, we have, 



the ratio of the two amplitudes is = — — -, 



n + v x — iv 2 



and putting this in the form .Re 1 *, we have 



2nv« 



<£ = tan -1 



n" — v x 



so that the change of phase of the reflected light is, when repre- 

 sented as a time, 



1 . . 2nv. 

 -tan -1 — ■ 



p n* — Vi — v£ ' 



Now from equation (3), since a = a + ib, and ty = — , 



, , a \pi A- 



b r + 2vm - -y = I 



Suppose the plane of incidence is that of zx, containing the 

 direction of the current. 



