520 Mr Qamphell, DiscoiHinuities in Light Eviission. 



be accepted (and its author holds it to be compatible with the 

 spherical wave theory), the measurements on the photoelectric 

 effect in zinc, quoted in the former paper, indicate that the 

 number of electrons which can be liberated from zinc by a single 

 light disturbance is about 3, and the number of such electrons 

 is likely to be of the same order of magnitude in the case of the 

 alloy of sodium and potassium. But, on the same theory, the 

 fraction of that number which are liberated within any given 

 photoelectric cell is the solid angle subtended by the surface of 

 the cell at the source. 



In our case this solid angle was never as much as ^, and 

 hence, on this theory, to should be considerably less than unity 

 and 7f large compared with &>. It should be expected therefore 

 that, whichever of the two theories of light emission is true, 

 6rp'^ should be proportional to the intensity simply. If Planck's 

 theory be not accepted, there is no apparent method of calculating 

 the number of electrons liberated by a single disturbance. 



Table I. 



160 volts on Electrometer Needle, i and R are given in electro- 

 static units, 6,^' in scale divisions. The value of the last quantity is 

 deduced from not less than 300 observations in each case. 



^y'Vt^ = 0-0068 0-0103 0-0180 



