THE ALKALI METAL f'UOTOELECTRIC CELL 329 



significant difference in the total emission trom a really rough surface 

 when the plane of polarization of the incident light is changed; and 

 such in fact is the case. We would also expect tiiat (he distribution 

 of response according to wave length would be a mixture of the effects 

 of the two planes of polarization. This also is found to be so. Rough 

 surfaces show the wave length maximum characteristic of light polar- 



pig 9 — Wave-length distribution of emission from rough surface potassium photo- 

 electric cells, showing variation from cell to cell depending on difference of treatment. 



ized with the electric vector in the plane of incidence on a specular 

 surface. Depending on the degree of roughness and the method of 

 preparation of the surface, the wave length maximum is different in 

 size and also in position. In Figure 9 are shown several wave length 

 distribution curves for potassium cells in which the surface is roughened 

 and colored by a hydrogen glow discharge. These cells differ both in 

 respect to their absolute sensitiveness, in the position of their maxi- 

 mum sensitiveness, and the extent of their sensitiveness toward the 

 red end of the spectrum. It has not as yet been found possible to pre- 

 pare photoelectric cells with properties uniform from one cell to another. 



