﻿Scattering 
  of 
  a 
  Particles 
  by 
  Gases. 
  

  

  709 
  

  

  be 
  seen 
  later, 
  that 
  the 
  scattering 
  coefficient 
  varied 
  inversely 
  

   as 
  the 
  fourth 
  power 
  of 
  the 
  velocity. 
  In 
  practice, 
  the 
  value 
  

   of 
  the 
  pressure 
  was 
  corrected 
  so 
  as 
  to 
  give 
  the 
  scattering 
  

   observed, 
  assuming 
  that 
  the 
  velocity 
  was 
  equal 
  throughout 
  

   to 
  the 
  initial 
  value 
  for 
  the 
  « 
  particle. 
  

  

  Variation 
  of 
  scattering 
  with 
  velocity. 
  

  

  Geiger 
  found 
  that 
  the 
  most 
  probable 
  angle 
  of 
  scattering 
  of 
  

   a 
  particles 
  by 
  solid 
  matter 
  increased 
  rapidly 
  with 
  decrease 
  

   of 
  velocity 
  of 
  the 
  « 
  particle. 
  This 
  also 
  holds 
  for 
  light 
  gases. 
  

   The 
  initial 
  velocity 
  of 
  the 
  a 
  particle 
  was 
  diminished 
  by 
  

   placing 
  a 
  sheet 
  of 
  aluminium 
  foil 
  of 
  known 
  stopping 
  power 
  

   under 
  the 
  active 
  wire. 
  The 
  results 
  are 
  shown 
  in 
  fig. 
  4, 
  

  

  Fig. 
  4. 
  

   Pressure 
  in 
  cms. 
  

  

  2 
  H 
  6 
  8 
  10 
  12 
  

  

  V 
  

  

  

  

  

  

  

  \v 
  

  

  

  

  

  

  

  \ 
  x 
  

  

  >v 
  

  

  

  

  

  

  \ 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  \a 
  

  

  

  

  B 
  

  

  

  

  

  

  

  

  

  ^^O 
  

  

  

  

  

  

  

  X 
  

  

  

  

  

  

  

  

  e? 
  

  

  ' 
  2 
  4 
  6 
  8 
  10 
  I? 
  

  

  Pressure 
  in 
  cms. 
  

  

  where 
  the 
  logarithm 
  of 
  the 
  corrected 
  ionization 
  in 
  the 
  testing- 
  

   vessel 
  is 
  plotted 
  as 
  ordinates 
  and 
  pressures 
  as 
  abscissse. 
  In 
  

   curve 
  A, 
  the 
  initial 
  velocity 
  was 
  the 
  maximum 
  velocity 
  of 
  

   a. 
  particles 
  from 
  radium 
  C, 
  whilst 
  in 
  curve 
  B 
  the 
  initial 
  

   velocity 
  was 
  '893 
  of 
  the 
  maximum 
  velocity. 
  The 
  scattering 
  

   coefficients 
  observed 
  in 
  the 
  two 
  cases 
  were 
  in 
  the 
  ratio 
  

   1 
  : 
  1*66. 
  The 
  scattering 
  thus 
  varied 
  approximately 
  as 
  the 
  

   Phil. 
  Mag. 
  S. 
  6. 
  Vol. 
  26. 
  No. 
  154. 
  Oct. 
  1913. 
  3 
  B 
  

  

  