﻿566 
  

  

  On 
  the 
  Photoelectric 
  Effect, 
  

  

  The 
  most 
  serious 
  effect 
  of 
  this 
  overlapping 
  appears 
  in 
  the 
  

   case 
  of 
  caesium, 
  fig. 
  7. 
  Here 
  there 
  is 
  little 
  or 
  no 
  evidence 
  

   of 
  the 
  first 
  maximum, 
  which 
  theory 
  and 
  analogy 
  would 
  place 
  

   in 
  the 
  red 
  or 
  infra-red 
  part 
  of 
  the 
  spectrum 
  It 
  is 
  possible 
  

  

  Fie:. 
  8 
  

  

  that 
  the 
  maximum 
  lies 
  beyond 
  the 
  range 
  of 
  the 
  illuminator 
  

   and 
  the 
  mercury 
  arc. 
  If 
  it 
  should 
  lie 
  at 
  a 
  wave-length 
  

   longer 
  than 
  about 
  550 
  yuii 
  it 
  is 
  also 
  possible 
  that 
  it 
  would 
  be 
  

   masked 
  by 
  the 
  low 
  dispersive 
  power 
  of 
  the 
  instrument 
  in 
  

   this 
  region. 
  Thus 
  the 
  left 
  end 
  of 
  the 
  curve 
  is 
  unsatisfactory. 
  

   The 
  second 
  maximum 
  (b), 
  however, 
  is 
  shown 
  very 
  distinctly 
  

   and 
  is 
  at 
  a 
  wave-length 
  of 
  about 
  250 
  fifi. 
  

  

  Conclusion. 
  

  

  The 
  experimental 
  results 
  indicate 
  that 
  the 
  photoelectric 
  

   sensitiveness 
  is 
  the 
  same 
  function 
  of 
  the 
  frequency 
  for 
  all 
  

   metals, 
  the 
  difference 
  being 
  that 
  the 
  curve 
  is 
  shifted 
  bodily 
  

   out 
  to 
  the 
  region 
  of 
  short 
  wave-lengths 
  for 
  the 
  electronegative 
  

   metals. 
  This 
  function 
  is 
  evidently 
  not 
  that 
  expressed 
  by 
  

   equation 
  (6). 
  Equation 
  (6), 
  however, 
  accurately 
  predicts 
  

   the 
  values 
  of 
  X 
  an 
  d 
  X 
  max 
  ., 
  and 
  seems 
  to 
  be 
  at 
  least 
  a 
  part 
  of 
  

   the 
  truth. 
  

  

  It 
  will 
  be 
  remembered 
  that 
  earlier 
  in 
  the 
  paper 
  reference 
  

   was 
  made 
  to 
  the 
  fact 
  that 
  equation 
  (6) 
  is 
  only 
  one 
  solution 
  of 
  

   the 
  theoretical 
  equations, 
  and 
  that 
  it 
  is 
  probably 
  not 
  the 
  only 
  or 
  

   the 
  complete 
  solution. 
  The 
  results 
  of 
  this 
  investigation 
  point 
  

  

  