328 BELL SYSTEM TECHNICAL JOURNAL 



through the spectrum is as shown by the curve marked A. in Figure 8. 

 Photoelectric emission is entirely absent on the long wave side of a 

 certain wave length which is known as the long wave length limit. 

 From this wave length, the emission rises gradually and uniformly 

 toward the short wave or blue end of the spectrum. 



When the incident light is polarized so that the electric vector has a 

 component perpendicular to the surface, the wave length distribution 

 of response follows the general character shown in the curve marked 1 1 

 in Figure 8. Correlating the wave length distribution of response with 



WAVE LENGTH 



Fig. 8 — Wave-length distribution of response from specular alkali metal surface; 

 electric vector in plane of incidence (||); electric vector perpendicular to plane ot 



incidence ( x ). 



the variation of emission with the plane of polarization considered in 

 the last section, the general conclusion may be drawn that the enhanced 

 emission for light with the electric vector in the plane of incidence is 

 due largely to radiation falling within a narrow spectral region. The 

 magnitude of this wave length peak varies greatly with different 

 materials. The maximum occurs at a wave length different not only 

 for the different alkali metals, but also for different modes of securing 

 the specular surface. This wave length maximum has the appearance 

 of being due to some resonance phenomenon, and its variation in 

 position through the spectrum according to the method of preparation 

 of the surface is connected in some unknown wa}^ with the state of 

 binding of the alkali metal atom on the surface with the body of ma- 

 terial beneath. 



The Photoelectric Current from Rough Surfaces 



With rough surfaces of alkali metal, the plane of polarization of the 

 incident light no longer has meaning. We would therefore expect no 



