THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



AUGUST 1871. 



XL On the Reflection of Light from Transparent Matter. By 

 The Hon. J. W. Strutt, M.A., Fellow of Trinity College, 

 Cambridge*. 



IN connexion with other investigations on light I had occa- 

 sion to consider the problem of reflection, in order to see 

 how far the facts might be accounted for by the different hypo- 

 theses which have been made as to the condition of the aether in 

 transparent matter. Although, as I now find, some of the re- 

 sults then arrived at have been already given by Lorenz, of 

 Copenhagen, the publication of the present paper may not be 

 without use, as I cannot agree with him on many important 

 points, and great misapprehension seems to prevail on the sub- 

 ject generally. 



Starting with the assumption that the rigidity is the same in 

 the two media, and that the vibrations of light are normal to the 

 plane of polarization, Fresnel was led to the conclusion that if 

 the incident vibration be represented by unity, the reflected 

 vibration is given by the expressions 



sin (<9,-6>) tan(fl,-<9) 

 sin^ + fl)' tan(0, + 0)' 



according to whether the plane of primitive polarization coincides 

 with or is perpendicular to the plane of incidence. The process 

 by which the first (sine) formula is obtained is rigorous, or at 

 least may be made so by additional explanations. With regard 

 to the second, the reasoning cannot be considered demonstrative, 

 although, as a matter of fact, the arbitrary principle assumed 



* Communicated by the Author. 

 Phil. Mag. S. 4. Vol. 42. No. 278. Aug. 1871. G 



