306 



WRIGHT: INTERFERENCE FIGURES IN OBJECTIVES 



ent purposes it may be neglected. Having given the angle of rota- 

 tion B of the plane of vibration the problem resolves itself prac- 

 tically into a determination of the intensity of illumination for 

 the different parts of the visible spectrum for different relative 

 positions of the sensitive tint plate and the analyzer, the resulting 

 color being the integral result of the distribution of color intensity 

 over the entire visible spectrum. 



For this purpose the standard Fresnel intensity equation 



d{y' - a') 

 X 



/ = cos^ if -(- sin 2 ((/?-??) sin 2 ?? . sin- t 



(2) 



30 



Z 

 UJ 



U20 



a: 

 u 



Q. 



10 



> 



(/) 



z 

 111 



I- 

 z 



400 500 



WAVE 



600 700 800 



LENGTH IN fJifJi 



Fig. 2. The curves of this figure repre- 

 sent graphically the data of Table 1, 

 namely, the intensity of the light, in per 

 cent, for different wave lenths X after 

 transmission through the polarizer, sensi- 

 tive tint quartz plate (0.03 mm. thick cut 

 parallel to the optic axis which makes an 

 angle B with the vibration plane of the 

 polarizer) and the analyzer whose prin- 

 cipal plane includes an angle 4> with that 

 of the polarizer. 



is applicable, in which 1 is the 

 percentage intensity of illumina- 

 tion, if, the angle included be- 

 tween thetwonicols, ??, the angle 

 which the vibration direction 7 

 of the sensitive tint plate in- 

 cludes with the principal plane 

 of the analyzer, d the thickness 

 of the sensitive quartz plate 

 used, 7'- a', the birefringence of 

 the quartz sensitive tint plate 

 for the particular wave length 

 X of light employed. The re- 

 sults of computation by this 

 equation of the intensity of the 

 transmitted light for different 

 angles ^and ??, and wave lengths 

 X for a quartz plate 0.03 mm. 

 thick (thickness for the sensitive 

 tint whereby the path difference 

 for X = 550mm is half a wave 



length and sin' 



dW - ol') 



= 1) 



X 



cut parallel to the principal 

 axis are listed in Table 1 and 

 presented graphically in fig- 

 ure 2. 



