Reflexion from a Moving Mirror. 



283 



tube, which is perpendicular to the raj, and the electric 

 intensity perpendicular to that velocity, divided by c 2 , so that 



o or 

 = ] E. 



C 



Let 



where 



Then 



z — z sin m(x cos 6 + ?/ sin 6 + rt) , 

 .r cos + y sin # = r. 



E 



(2) 



(3) 



4 s 



= llmr cos m(#cos # + ?/ sin # + d)? 

 so that the amplitude of E is 



E = Rmz . . , . . . 

 Similarly, 



H. 



i!/«:„. 

 c 



(4) 



(5) 



Now if the waves are obliquely reflected by a moving 

 reflector, we have the following relations 



-frcostf sin 



m 



m 



C — vcobO sin 6' 



Further, 



2T + V = 



Combining the relations (4) ... (7), 



H ' _ E/ _ m sin 6 _c + vcos0 



H E t 



m 



am 6' c — vcosd r 



(6) 



(?) 



(») 



This result is independent of the plane of polarization, and 

 is in complete agreement with those of both Sir Joseph Larmor 

 and Mr. Edser. 



Equation (7) corresponds to the equation £ -f f' = quoted 

 originally by Mr. Edser, and z can be identified with the 

 sethereal displacement f. The continuity of the magnetic 

 force normal to the reflector of course follows from (8) when 

 the plane of polarization is such that the magnetic forces lie 

 in the plane of the reflector. It is also apparent that £ is not 



