236 SIR DAVID BREWSTER OX THE 



of incidence- The vanishing image is at its minimum when crossed half with blue 

 and half with red light. 



Light polarised + 45° — 45°. E' and 0' polarised simultaneously 82 c | to the 

 plane of incidence. Both have the same intensity, and are crossed at their 

 minimum with red and blue light. 



Light polarised 0° and 90°. Although E does not suffer reflexion from the 

 glass surface, yet E' is visible, and vanishes, along with 0', 82^° to the right of the 

 plane of incidence. 



Azimuth 218°, Obtuse angle to the Left. Common sun's light is completely 

 polarised 8° to the right of the plane of incidence. The evanescence is complete 

 at the polarising angle of 0, but not at greater angles. 



Light polarised 0° and 90°. E' and 0' are both polarised 8° to the right. E' 

 is bright yellow and 0' bright pink. 



Light polarised + 46° — 45°. E' and 0' are polarised 8° to the right, E' being 

 yellow and 0' blue. 



Azimuth 15° to the left. Light polarised Z and 90°. E' and 0' vanish together, 

 and 0' is polarised about 40° to the right. 



Light polarised +45° — 45°. Obtuse angle from the eye E' and 0' are 

 polarised 55° to the right. 



Azimuth 45°. Light polarised + 45~ — 45°. E' and 0' vanish completely at 

 polarising angle 92° to the right. The deviation is increased by increasing the 

 incidence. 



On the Intensity of the Reflected Pencil. 



Common Light, Azimuth 0° and 180°. The spar and oil image S is equal to 

 about I of the prism image P. 



Azimuth 45° and 215°. S = f P. 



Azimuth 90° and 270 c . S = P, P a little brighter. 



Light polarised + 45°— 45°. 



Azimuth 0° and 180°. 0' gradually diminishes and vanishes at 90°, while E 

 increases and is a maximum at 9 G . 



Azimuth 90° and 270°. E' is a maximum and nearly equal to 0', which almost 

 vanishes. 



Beyond 90° and 270°, 0' gradually increases while E' diminishes, and they 

 become equal at 180°. 



Light polarised 0° and 90°. Azimuth 0° and 180°. 0' almost vanishes, but 

 E" is bright, though only equal to £ P. O' increases gradually to azimuth 90°, 

 where it is equal to 0. 



Azimuth 90° and 270°. E'= 0', both pretty bright, but less so than P. 



Azimuth 123°. E' vanishes. 0' a little less than P. 



Azimuth 180°. 0' vanishes. E'=|P. 



