89 



University Studies 



Vol. V JANUARY 1905 No. 1 



I. — Electric Double-Refraction in Carbon Bisulphide at Low 



Potentials 



BY GUSTAF W, ELMEN 



When light polarized at an angle of forty-five degrees to the 

 lines of force is passed through certain dielectrics, between two 

 parallel electrodes, they become double-refracting. The differ- 

 ence of phase, S, between the two components of light at right 

 angles and parallel to the lines of force, as represented by Kerr 

 and verified by later investigators, is 



^ a'' 



where B is the electro-optic constant, depending on the dielectric, 

 / the length, and a the distance between the plate electrodes in 

 centimeters, and P the difference of potential between the elec- 

 trodes in C.G.S. units. 



From data obtained in this investigation, there seems to be a 

 decided variation from the above law for low potentials. As the 

 potential was decreased from about 200 volts per millimeter of 

 distance between the electrodes, the decrease of 8 was in a 

 smaller ratio than the decrease of P-. 



Tn determining the electro-optic constant, either a high poten- 

 tial or a sensitive system of measuring 8 must be used. In the 



University Studies, Vol. V, No. 1, January 1905. 



I 



