THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



MA Y 1874. 



XXXIX. On the Determination of the prime Angle of Incidence 

 and prime Azimuth for the different Fraunhofer's Lines. By 

 G. Quincke*. 



IF under the prime angle of incidence H linearly polarized 

 light be reflected from a plane surface, the plane of polar- 

 ization making the angle a, with the plane of reflection, the two 

 components polarized perpendicular and parallel to the plane of 

 incidence will have a difference of phase of a quarter wave-length, 

 and the ratio of their amplitudes is determined by the tangent 

 of the prime azimuth B, by the equation 



S _ tan B 



P~taT^ W 



The reflection is named positive when the component polarized 

 parallel to the reflection-plane is accelerated relatively to that 

 polarized perpendicular to that plane, negative when it is retarded. 

 The former case is the more frequent. With metals, positive 

 reflection only has yet been observed. 



If the prime angle of incidence and prime azimuth are known, 

 then from these the difference of phase and the ratio of the am- 

 plitudes, or the intensity of the components of the reflected 

 light, for any angle of incidence can be calculated by means of 

 formulae which, although of quite a different form and found in 

 a very different way, represent the phenomena equally well, 

 within the possible errors of observation. (Conf. Pogg. Ann. 

 vol. cxxviii. pp. 387-399, 541-564. 1866; vol. cxxxvi. p. 585. 

 1869.) 



* Translated from a separate impression, communicated by the Author. 

 Phil. Mag. S. 4. Vol. 47. No. 313. May 1874. Y 



