﻿912 
  Dr. 
  J. 
  P. 
  V. 
  Madsen 
  on 
  the 
  

  

  § 
  III. 
  Results 
  of 
  Experiments. 
  

  

  Fig. 
  3 
  (PL 
  XXX.) 
  shows 
  the 
  results 
  of 
  experiments 
  per- 
  

   formed 
  with 
  the 
  apparatus 
  of 
  fig. 
  1, 
  using 
  Al 
  screens. 
  

  

  Curves 
  D 
  and 
  E 
  give 
  the 
  currents 
  for 
  different 
  thicknesses 
  

   of 
  screen, 
  with 
  the 
  screens 
  in 
  the 
  positions 
  A 
  and 
  C 
  respec- 
  

   tively. 
  The 
  abscissae 
  represent 
  grammes 
  per 
  square 
  cm. 
  from 
  

   which 
  the 
  thickness 
  of 
  screen 
  may 
  be 
  immediately 
  deduced, 
  

   knowing 
  its 
  density. 
  

  

  Curve 
  C 
  is 
  obtained 
  by 
  subtracting 
  the 
  values 
  of 
  D 
  and 
  

   E 
  corresponding 
  to 
  any 
  screen, 
  and 
  is 
  a 
  measure 
  of 
  the 
  total 
  

   amount 
  of 
  emergent 
  scattered 
  radiation. 
  

  

  It 
  will 
  be 
  seen 
  from 
  fig. 
  1 
  that 
  the 
  whole 
  of 
  the 
  scattered 
  

   radiation 
  is 
  not 
  quite 
  included, 
  as 
  the 
  effects 
  are 
  somewhat 
  

   interfered 
  with 
  by 
  geometrical 
  conditions. 
  When, 
  for 
  example, 
  

   the 
  screen 
  was 
  brought 
  nearer 
  the 
  Pa 
  than 
  C 
  a 
  slight 
  rise 
  

   was 
  observed 
  in 
  the 
  reading. 
  The 
  intensity 
  of 
  the 
  radiation 
  

   falling 
  on 
  the 
  screen 
  was 
  slightly 
  increased 
  owing 
  to 
  some 
  

   of 
  the 
  more 
  oblique 
  rays 
  from 
  the 
  Pa 
  being 
  now 
  able 
  to 
  fall 
  

   upon 
  the 
  screen. 
  

  

  Curves 
  A 
  and 
  B 
  represent 
  the 
  results 
  of 
  subtracting 
  

   readings 
  with 
  the 
  screen 
  at 
  B 
  and 
  C 
  and 
  A 
  and 
  B 
  respec- 
  

   tively 
  (fig. 
  1), 
  and 
  are 
  measures 
  of 
  the 
  amount 
  of 
  radiation 
  

   slightly 
  deflected, 
  and 
  of 
  that 
  v/hich 
  has 
  suffered 
  much 
  larger 
  

   deflexion. 
  

  

  Curve 
  F 
  represents 
  the 
  returned 
  radiation 
  from 
  aluminium 
  

   screens 
  of 
  different 
  thicknesses. 
  Similar 
  curves 
  to 
  the 
  above 
  

   are 
  shown 
  in 
  fig. 
  4 
  for 
  Au 
  screens. 
  

  

  § 
  IV. 
  Discussion 
  of 
  Results. 
  

  

  In 
  fig. 
  3, 
  from 
  curve 
  C, 
  it 
  is 
  seen 
  that 
  the 
  total 
  emergent 
  

   scattered 
  radiation 
  increases 
  rapidly 
  to 
  a 
  maximum, 
  and 
  then 
  

   steadily 
  decreases 
  as 
  the 
  thickness 
  of 
  screen 
  is 
  increased. 
  

   The 
  maximum 
  occurs 
  at 
  about 
  '013 
  cm. 
  

  

  Comparing 
  the 
  curves 
  C 
  and 
  F, 
  it 
  is 
  seen 
  that 
  for 
  thin 
  

   screens 
  the 
  emergent 
  is 
  much 
  greater 
  than 
  the 
  incident 
  

   scattered 
  radiation 
  The 
  greatest 
  value 
  of 
  the 
  ratio 
  is 
  about 
  

   9:1. 
  

  

  Comparing 
  the 
  similar 
  curves 
  for 
  Au, 
  fig. 
  4, 
  it 
  is 
  again 
  

   seen 
  that 
  a 
  considerable 
  lack 
  of 
  symmetry 
  exists 
  between 
  

   emergence 
  and 
  incidence 
  radiation, 
  though 
  not 
  so 
  marked. 
  

   In 
  this 
  case 
  the 
  greatest 
  value 
  of 
  the 
  ratio 
  is 
  about 
  4*5 
  : 
  L 
  

   The 
  maximum 
  for 
  the 
  emergence 
  radiation 
  is 
  reached 
  at 
  

   about 
  -0008 
  cm. 
  

  

  The 
  effects 
  of 
  scattering 
  in 
  the 
  case 
  of 
  B 
  rays 
  are 
  thus 
  

   very 
  similar 
  to 
  those 
  observed 
  for 
  7 
  rays, 
  a 
  material 
  of 
  high 
  

  

  