714 Sir J. J. Thomson on some Optical Effects 



T r 



Let co = t , ' 



c 



as throughout the integration t is constant 

 dr = —c . dco. 



Since at the same instant the accelerations of all the 

 electrons in the slab are equal, 



\ c 



hence Y 1 = — eaD \ ' ' dco 



c 



^r d fr\ 



— eaD 



c L 



<i«J 



The limits of co are t where a' = OP, and t where 



c c 



R is the greatest value o£ PQ ; when R is so large that 

 t— ~R/c corresponds to a time before the electrons began to 

 be affected by the light wave, 



®> 



so that Y^-^^D^ 



c \dco/t-~ 



— eaD.v^ * 



where v x is the velocity of an electron parallel to y at the 



c 



time t— xlc. lik = — eaD, we have 

 c 



Y l=~ kv t x (1) 



c 



Similarly Z : the force parallel to z will be given by 



Z^-k 



w 



where w . z is the velocity of an electron parallel to z at the 



time t . 



c 



