420 



WRIGHT— POLARIZED LIGHT IN THE 



polarized; the azimuth p of the plane of polarization of the reflected 

 wave is for Es^^Ep or tan €= i (equation 32) 



Rs 2(«2 — Wi) 

 tan p = ^^ = — I + -, , — TT r 



Rp (Wi + l)(W2 - i) 



(33) 



There is therefore on reflection a rotation of the plane of polar- 

 ization through the angle (e — p). For the ordinary case tan e^i 

 (e = 45°), we find from (33) 



tan (e — p) = 



I — tan p Hin^ — i 

 I -f tan p 712 — fii 



(34) 



The angular amounts of rotation on reflection of vertically inci- 

 dent plane-polarized light for e = 45° and for different refractive 

 indices and birefringences are listed in Table 4 and are presented 

 graphically in Fig. 3. 



TABLE 4. 



In this table is given the angular rotation, on reflection from a crystal 

 plate, of the plane of polarization of vertically incident light waves whose 

 plane of polarization includes an angle of 45° with the vibration directions of 

 the crystal plate. 



Figures 2 and 3 indicate clearly that there are two distinct meth- 

 ods for detecting anisotropism in birefracting, transparent media by 

 means of vertically incident light ; either intensity differences be- 

 tween the two components parallel and normal to the plane of inci- 

 dence may be utilized (equation 31) or the rotation of the plane of 

 polarization (equation 34). 



Differences of intensity are detected ordinarily by photometric 



