166 
PHYSICS: D. L. WEBSTER 
frequency in terms of the total energy radiated. In this case only a few of 
the electrons radiating will do so at frequencies very near the limit, V/H^ 
though more will radiate there than in an equal frequency interval at a fre- 
quency not too far below that one. Adopting this conclusion, the chance 
that an electron radiates a fraction of its energy within a range e to e + 
is/(F, €)de, where 
f^'^'^^^Wh V. • 
Let R be the radius of the atom and r the distance from the particle causing 
radiation to the path the electron would have taken if not deviated. Then 
or 
= - f(V,e)d e, with e = 1 at r = 0, 
1 
If we assumed the frequency to be determined by the energy transferred 
in a collision of two equal repelling particles, one of which was initially at rest, 
a definite value of v could be predicted for any assumed values of r and F, 
and the forms oi f{V, e) and i{V, v) could be found. Several such assumptions 
have been tried, but none give the forms of / and i required above. A de- 
tailed discussion would be out of place with such rough preliminary data, 
and any such assumption would be improbable, but it seems Hkely that more 
exact data of this type ought to throw valuable light on the mechanism of 
radiation. It is hoped that with apparatus now being constructed it wiU be 
possible to get such data. 
1 Beatty, R. T., Proc. Roy. Soc, London, A 89, 1913, (314-27). 
2 Webster, D. L., these Proceedings, 2, 1916, (90-4); Physic. Rev., Ithaca, 9, 1916, 
(599-613). 
3 Webster, D. L., and Clark, H., these Proceedings, 3, 1917, (181-5). 
4 Hull, A. W., Amer. J. Roentgenology 2, 1915, (893-9). 
5 Hull, A. W., and Rice, M., these Proceedings, 2, 1916, (265-70). 
^Ulrey, C. T., Physic. Rev., Ithaca, 11, 1918, (401-10). 
7 Webster, D. L., Ibid., 9, 1917, (220-5). 
