﻿Absorption 
  of 
  the 
  <y 
  Rays 
  of 
  Radium. 
  619 
  

  

  about 
  45 
  per 
  cent, 
  that 
  of 
  iron. 
  The 
  scattered 
  radiation 
  from 
  

   the 
  lead 
  was 
  actually 
  found 
  to 
  be 
  about 
  40 
  per 
  cent, 
  of 
  that 
  

   from 
  the 
  iron. 
  

  

  Now 
  consider 
  Table 
  II. 
  (b). 
  In 
  this 
  case 
  the 
  scattered 
  

   radiation 
  leaves 
  the 
  radiator 
  from 
  the 
  same 
  side 
  as 
  the 
  

   primary 
  rays 
  enter 
  and 
  makes 
  about 
  the 
  same 
  angle 
  with 
  the 
  

   normal. 
  Assuming 
  the 
  radiators 
  to 
  be 
  thick 
  enough 
  to 
  give 
  

   the 
  maximum 
  amount 
  of 
  scattered 
  radiation, 
  the 
  intensity 
  of 
  

   scattered 
  radiation 
  will 
  be 
  approximately 
  proportional 
  to 
  

   plfji 
  + 
  X, 
  p, 
  //,, 
  and 
  X 
  having 
  the 
  same 
  meaning 
  as 
  before. 
  

  

  For 
  carbon 
  p 
  = 
  l'68, 
  /x 
  = 
  0-074, 
  X=0"132, 
  

  

  p/ 
  f 
  i 
  + 
  \ 
  = 
  8'2; 
  

   „ 
  iron 
  /s 
  = 
  7-7, 
  ^ 
  = 
  0-30, 
  A, 
  = 
  0'75, 
  

  

  plfi 
  + 
  \=7'''3'; 
  

   „ 
  lead 
  / 
  o 
  = 
  ll-4, 
  ^ 
  = 
  0-56, 
  X 
  = 
  6'90, 
  

  

  p//j, 
  + 
  \=l'5 
  ; 
  

  

  or 
  about 
  5 
  times 
  as 
  much 
  radiation 
  should 
  escape 
  from 
  the 
  

   carbon 
  andiron 
  radiators 
  as 
  from 
  the 
  lead 
  radiator 
  ; 
  and 
  this 
  

   is 
  what 
  is 
  found 
  experimentally. 
  The 
  quantity 
  scattered 
  is 
  

   therefore 
  approximately 
  independent 
  of 
  the 
  radiator. 
  

  

  2. 
  The 
  quality 
  of 
  the 
  radiation 
  scattered 
  depends 
  on 
  the 
  

   angle 
  of 
  scattering, 
  and 
  not 
  on 
  the 
  nature 
  of 
  the 
  radiator. 
  

  

  The 
  tables 
  show 
  very 
  well 
  Florance' 
  s 
  result 
  that 
  the 
  greater 
  

   the 
  angle 
  of 
  scattering 
  the 
  softer 
  the 
  radiation. 
  Florance 
  

   found 
  that 
  after 
  the 
  rays 
  passed 
  through 
  6 
  millimetres 
  of 
  

   lead 
  the 
  quality 
  of 
  the 
  scattered- 
  radiation 
  was 
  approximately 
  

   independent 
  of 
  the 
  radiator. 
  In 
  the 
  present 
  case, 
  the 
  rays 
  

   from 
  the 
  lead 
  radiator 
  are 
  on 
  the 
  whole 
  more 
  penetrating, 
  

   but 
  this 
  is 
  mainly 
  due 
  to 
  the 
  much 
  greater 
  absorption 
  of 
  the 
  

   softer 
  rays 
  in 
  the 
  lead 
  radiator. 
  

  

  3. 
  The 
  softer 
  the 
  y 
  radiation 
  the 
  greater 
  the 
  percentage 
  

   of 
  it 
  scattered 
  per 
  unit 
  mass. 
  

  

  It 
  is 
  well 
  known 
  that 
  when 
  the 
  7 
  rays 
  of 
  radium 
  pass 
  

   through 
  lead 
  they 
  become 
  on 
  the 
  whole 
  more 
  penetrating. 
  

   (See 
  .figures 
  for 
  intensity 
  of 
  primary 
  rays.) 
  As 
  the 
  primary 
  

   rays 
  are 
  " 
  hardened/' 
  the 
  scattered 
  radiation 
  should 
  become 
  

   more 
  penetrating. 
  This 
  has 
  been 
  proved 
  by 
  Madsen 
  and 
  

   Florance, 
  and 
  can 
  be 
  seen 
  in 
  Tables 
  I. 
  and 
  II. 
  If 
  the 
  softer 
  

   rays 
  are 
  scattered 
  more 
  per 
  unit 
  mass 
  than 
  the 
  harder 
  rays, 
  

   and 
  we 
  compare 
  the 
  intensity 
  of 
  the 
  scattered 
  radiation 
  with 
  

   that 
  of 
  the 
  primary, 
  the 
  ratio 
  of 
  the 
  two 
  should 
  decrease 
  as 
  

   the 
  rays 
  become 
  " 
  harder." 
  The 
  ratio 
  does 
  decrease 
  ; 
  e. 
  g. 
  

   when 
  the 
  primary 
  rays 
  pass 
  through 
  a 
  lead 
  screen 
  1*29 
  cm. 
  

   thick, 
  the 
  intensity 
  of 
  the 
  scattered 
  rays 
  from 
  carbon 
  is 
  

  

  