ELLIPTIC POLARIZATION. 195 



The fundamental difference between this theory, and that 

 of Fresnel, consists (we have seen) in including a change of 

 phase of the reflected vibration, varying with the incidence. 

 This change of phase is due, according to M. Cauchy and 

 Mr. Green, to the normal vibration, which though evanes- 

 cent at a short distance from the surface modifies the 

 phase. 



(207) Professor Haughton has followed up the researches 

 so ably commenced by M. Jamin, and has obtained some new 

 and interesting results. The more important of these are 

 comprised in the following laws : 



I. If plane-polarized light be incident on a transparent 

 reflecting body, and the incidence be gradually increased 

 from to 90, the ratio of the axes of the reflected ellipti- 

 cally-polarized light diminishes from infinity, at 0, to a 

 minimum at the principal incidence ; and increases again to 

 infinity at 90. 



II. The minimum ratio of the axes varies with the plane 

 of polarization of the incident light, and diminishes as the 

 azimuth of that plane increases, until the latter reaches a cer- 

 tain value ; after which the ratio again increases. 



III. When the azimuth of the plane of polarization of 

 the incident light reaches this jalue, the ratio of the axes 

 becomes equal to unity, and the reflected light is circularly 

 polarized. 



This last conclusion is one which might have been antici- 

 pated. M. Jamin had shown that the difference of phase of 

 the two principal components of the reflected light was equal 

 to 270, at the principal incidence ; so that the light reflected 

 at this incidence must be circularly-polarized, when the am- 

 plitudes of the two components are equal. This equalization 

 of the reflected components can always be effected by varying 

 the azimuth of the plane of polarization of the incident ray. 



o2 



