﻿Scattering 
  of 
  the 
  /3 
  Rays 
  of 
  Radium. 
  913 
  

  

  atomic 
  weight 
  being 
  able 
  to 
  turn 
  back 
  in 
  the 
  process 
  of 
  

   scattorinor 
  more 
  of 
  the 
  oriorinal 
  radiation 
  than 
  a 
  material 
  of 
  

   smaller 
  atomic 
  weight. 
  

  

  Comparing 
  curves 
  A 
  and 
  B, 
  it 
  is 
  observed 
  that 
  A 
  reaches 
  

   a 
  maximum 
  sooner 
  than 
  B. 
  A 
  more 
  careful 
  examination 
  of 
  

   A 
  and 
  B 
  for 
  smaller 
  thicknesses 
  of 
  screen 
  has 
  shown 
  that 
  

   the 
  ratio 
  of 
  A 
  to 
  B 
  is 
  practically 
  constant 
  until 
  about 
  one- 
  

   third 
  of 
  the 
  maximum 
  reading 
  is 
  reached^, 
  after 
  which 
  the 
  

   ratio 
  gradually 
  decreases. 
  It 
  would 
  appear 
  that 
  while 
  the 
  

   ratio 
  remains 
  constant 
  we 
  are 
  concerned 
  with 
  only 
  a 
  single 
  

   collision 
  of 
  any 
  yS 
  particle, 
  that 
  as 
  the 
  screen 
  is 
  further 
  

   thickened 
  it 
  becomes 
  possible 
  for 
  a 
  /3 
  particle 
  to 
  suffer 
  more 
  

   than 
  one 
  collision 
  before 
  emerging, 
  thus 
  making 
  the 
  emergent 
  

   beam 
  appear 
  to 
  gradually 
  swing 
  round 
  from 
  its 
  original 
  

   direction, 
  a 
  greater 
  thickness 
  of 
  screen 
  being 
  required 
  to 
  

   produce 
  the 
  maximum 
  intensity 
  for 
  very 
  oblique 
  rays 
  than 
  

   for 
  those 
  corresponding 
  more 
  nearly 
  with 
  the 
  direction 
  of 
  

   the 
  original 
  stream. 
  

  

  A 
  fuller 
  consideration 
  of 
  the 
  effects 
  of 
  scattering 
  and 
  

   absorption 
  for 
  very 
  thin 
  films 
  will 
  be 
  reserved 
  for 
  a 
  future 
  

   paper. 
  

  

  A 
  theory 
  of 
  scattering 
  similar 
  to 
  that 
  proposed 
  by 
  Sir 
  

   J. 
  J. 
  Thomson 
  in 
  ' 
  Conduction 
  of 
  Electricity 
  through 
  Gases 
  ' 
  

   seems 
  capable 
  of 
  explaining 
  the 
  observed 
  results. 
  The 
  near- 
  

   ness 
  of 
  approach 
  of 
  a 
  /3 
  ray 
  to 
  a 
  constituent 
  of 
  an 
  atom 
  will 
  

   determine 
  the 
  amount 
  and 
  nature 
  of 
  the 
  deflexion 
  experienced, 
  

   the 
  speed 
  of 
  the 
  ^ 
  ray 
  and 
  the 
  constitution 
  of 
  any 
  particular 
  

   atom 
  being 
  also 
  necessary 
  factors. 
  

  

  Until 
  a 
  /3 
  ray 
  is 
  subject 
  to 
  more 
  than 
  one 
  collision 
  the 
  

   distribution 
  is 
  approximately 
  constant 
  for 
  a 
  given 
  material, 
  

   the 
  intensity 
  of 
  the 
  radiation 
  deflected 
  by 
  an 
  angle 
  6 
  from 
  

   the 
  original 
  direction 
  being 
  a 
  function 
  of 
  that 
  angle 
  for 
  any 
  

   one 
  material 
  and 
  with 
  rays 
  of 
  a 
  given 
  quality. 
  

  

  We 
  are 
  to 
  consider 
  this 
  function 
  of 
  6 
  as 
  being 
  different 
  

   for 
  the 
  different 
  atoms. 
  

  

  The 
  lack 
  of 
  symmetry 
  in 
  the 
  distribution 
  of 
  scattered 
  

   X-rays 
  has 
  been 
  shown 
  by 
  Bragg*, 
  and 
  assuming, 
  as 
  seems 
  

   reasonable 
  on 
  many 
  grounds, 
  that 
  X- 
  and 
  7-rays 
  are 
  of 
  the 
  

   same 
  nature, 
  it 
  appears 
  from 
  that 
  investigation 
  that 
  the 
  softer 
  

   radiation 
  shows 
  less 
  want 
  of 
  symmetry 
  when 
  falling 
  on 
  a 
  

   given 
  material 
  than 
  does 
  the 
  harder. 
  

  

  Xow 
  although 
  the 
  lack 
  of 
  symmetry 
  shown 
  by 
  the 
  scattered 
  

  

  /3 
  rays 
  is 
  much 
  greater 
  than 
  that 
  found 
  for 
  7- 
  and 
  X-rays, 
  

  

  even 
  though 
  the 
  former 
  are 
  less 
  penetrating, 
  the 
  general 
  

  

  nature 
  of 
  the 
  effect 
  has 
  been 
  shown 
  to 
  be 
  much 
  the 
  same 
  in 
  

  

  * 
  Trans. 
  Roy. 
  Soc. 
  S. 
  A. 
  vol. 
  xxxii. 
  (1908). 
  

  

  