PROF. C. G. BARKLA ON X-RAYS AND THE THEORY OF RADIATION. 
341 
one quantum of K radiation is emitted for each K electron expelled whatever be the 
velocity of its ejection. 
Table V. 
# 
Approximate wave-length of primary 
X-radiation. 
Number of quanta of K fluorescent 
radiation emitted per Iv electron ejected. 
cm. 
0-87 x10-« 
1-09 
0-71xlO- 8 
0-95 
0-56 xlO" 8 
0-85 
0-49 x10 _s 
0-81 
0-35 xlO" 8 
0-90 
The variations from unity are irregular and obviously may be the result of 
observational or experimental errors. The maximum variation of 19 per cent, is 
small considering the number and nature of the experimental determinations involved. 
Apart from a quantum theory, the range of possible values is so enormous in com¬ 
parison with the variation observed that the emission of one quantum of characteristic 
X-radiation for each electron in the associated corpuscular radiation must be regarded 
as an experimentally established fact. It is a fact of some significance. 
Less accurate experiments on other substances lead to a similar conclusion approxi¬ 
mately if not accurately. There is no reason to think the results would be less 
convincing. The fundamental physical truth one cannot for a moment question, 
though it is possible that certain conditions would produce greater irregularities than 
are exhibited above. 
First Approximation to Energy Relations. 
If the two K secondary radiations—the corpuscular and the characteristic X-radia¬ 
tion—together accounted for the whole of the K energy absorbed, we should have of 
the energy of the primary beam absorbed as K absorption, the fraction 
n + n-f 
or 
Mk 
\ 
re-emitted as K corpuscular radiation, and the fraction 
Hz. 
n + m 
or 
n 
n + r-K 
m kI 
as K fluorescent X-radiation. 
It has been shown that when /u is somewhat less than // K , i.e., when //. = 0'84^ K , 
about 42 per cent, of the energy of the primary radiation specially absorbed in bromine 
appears to be re-emitted as fluorescent X-radiation of series K, while about 46 per 
cent, is re-emitted in the K corpuscular radiation. Thus the two together account 
for about 88 per cent, of the primary radiation. Also as /m. diminishes, the two 
energies of fluorescent and corpuscular radiations remain approximately comple¬ 
mentary, the energy of the former diminishing while that of the other increases. 
Table VI. gives the experimentally determined values of 
3 b 2 
