﻿Kinetic 
  Energy 
  of 
  the 
  Ions 
  emitted 
  by 
  Hot 
  Bodies. 
  891 
  

  

  narrow 
  gap 
  in 
  the 
  infinite 
  conducting 
  plane 
  B. 
  At 
  a 
  short 
  

   distance 
  from 
  B, 
  and 
  parallel 
  to 
  it, 
  is 
  another 
  infinite 
  con- 
  

   ducting 
  plane 
  CD 
  divided 
  into 
  two 
  portions 
  by 
  a 
  narrow 
  slit 
  

   parallel 
  to 
  the 
  edges 
  of 
  A. 
  A 
  and 
  B 
  are 
  charged 
  to 
  the 
  

   same 
  potential 
  and 
  the 
  resulting 
  current 
  to 
  the 
  plane 
  CD 
  is 
  

   measured. 
  Simultaneously 
  the 
  ions 
  which 
  pass 
  through 
  the 
  

   slit 
  are 
  measured 
  by 
  means 
  of 
  the 
  box-shaped 
  electrode 
  E. 
  

   The 
  whole 
  system 
  CED 
  can 
  be 
  pushed 
  along 
  bodily 
  by 
  a 
  fine 
  

   screw 
  and 
  the 
  current 
  through 
  the 
  slit 
  is 
  compared 
  with 
  the 
  

   sum 
  of 
  the 
  currents 
  to 
  the 
  plates 
  CD 
  and 
  the 
  slit, 
  for 
  a 
  series 
  

   of 
  positions 
  of 
  the 
  latter. 
  In 
  this 
  way 
  a 
  curve 
  is 
  obtained 
  

   which 
  gives 
  the 
  fraction 
  of 
  the 
  total 
  current 
  passing 
  through 
  

   the 
  slit 
  in 
  any 
  position. 
  The 
  curve 
  on 
  the 
  left 
  in 
  fig. 
  2 
  has 
  

   been 
  obtained 
  in 
  this 
  way. 
  If 
  the 
  emitted 
  ions 
  possessed 
  no 
  

   sideways 
  velocity 
  this 
  curve 
  would 
  consist 
  of 
  one 
  horizontal 
  

  

  Fie:. 
  2. 
  

  

  

  

  

  

  

  

  

  

  

  

  

  %' 
  

  

  ■%' 
  

  

  

  

  

  

  

  

  

  

  

  

  

  \ 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  / 
  

  

  > 
  

  

  

  

  

  

  

  

  

  

  

  / 
  

  

  / 
  

  

  

  

  

  

  

  \ 
  

  

  V 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  \ 
  

  

  

  

  

  

  

  

  

  

  

  

  

  u. 
  

  

  *>' 
  \ 
  

  

  7 
  3 
  9 
  10 
  II 
  12 
  

  

  <Sc/>t£ 
  or 
  x(/= 
  -0635 
  cm) 
  

  

  and 
  two 
  inclined 
  straight 
  lines, 
  as 
  shown 
  on 
  the 
  right. 
  Since 
  

   it 
  does 
  not 
  do 
  so 
  it 
  follows 
  that 
  the 
  ions 
  are 
  emitted 
  with 
  a 
  

   finite 
  sideways 
  velocity. 
  

  

  Let 
  us 
  see 
  how 
  the 
  form 
  of 
  these 
  curves 
  depends 
  on 
  the 
  

   distribution 
  of 
  velocity 
  among 
  the 
  ions. 
  Let 
  the 
  figure 
  (fig. 
  1) 
  

   lie 
  in 
  the 
  plane 
  of 
  asz, 
  the 
  axis 
  of 
  z 
  being 
  perpendicular 
  to 
  

   B 
  and 
  CD. 
  Consider 
  an 
  ion 
  whose 
  coordinates 
  at 
  any 
  instant 
  

   are 
  x, 
  y, 
  z. 
  Let 
  the 
  plane 
  of 
  A 
  be 
  the 
  plane 
  2=0. 
  The 
  

   electric 
  field 
  between 
  A 
  and 
  CD 
  is 
  uniform 
  and 
  equal 
  to 
  Z. 
  

  

  