﻿common Light obliquely incident on parallel plates. 213 



This latter portion forms a part of the total beam reflected by 

 the two plates. 



Summing up the reflected and refracted portions, we get the 

 intensity of the reflected beam 



= P 2 + i(l-X; 2 ) 2 .-{l + A 4 + F+&c.} 



~2 L l + A a J~2 1 + * 8 -l + 3t; a ' 

 The intensity of the refracted beam is 



l (1 _^. {1 + ^ + , 3 + & c. } = |.^| = i.i^, 



We may in the same way determine the intensities of beams 

 reflected from successive plates ; and it will readily be seen that 

 the intensity of the reflected beam is 



1 2mv* 



2 l + (2m-l>; 2 

 and the intensity of the refracted beam 



_1 1-tt 2 



~2* l + (2m-iy' 



where m is the number of plates. 



If we consider the beam polarized in the plane at right angles 

 to the plane of incidence, the reflected portion will be 



1 2mw 2 



2*1 + (2m- 1)^' 



and the refracted portion 



1 1-w 2 



~~ 2 l + (2m-l)w 2 



The intensity of polarized light in each beam is 



1 f 1-w 2 1-t; 2 7 



2 \_l + (2m-l)w z l + {2m-l)v*J ' 



2jYL1Ij 



the intensity of natural light reflected being ^ — > 2 , and 



1— v 2 



refracted being -, , ^r^. 



D 1 + (2m — ljir 



Let j^and n represent the proportions of polarized and natural 

 light in the refracted beam, then 



