﻿the 
  Photoelectric 
  Effect. 
  

  

  563 
  

  

  (curve 
  1). 
  Curve 
  2 
  is 
  the 
  graph 
  of 
  equation 
  (6), 
  reckoned 
  

   for 
  aluminium, 
  N 
  being 
  expressed 
  in 
  arbitrary 
  units. 
  The 
  

   readings 
  for 
  curve 
  3 
  were 
  taken 
  72 
  hours 
  after 
  those 
  for 
  

   curve 
  1. 
  The 
  shrinkage 
  represents 
  the 
  photoelectric 
  fatigue 
  

   during 
  this 
  interval. 
  Curves 
  4 
  and 
  5 
  were 
  taken 
  under 
  the 
  

   same 
  conditions 
  as 
  curve 
  1, 
  except 
  that 
  the 
  strip 
  S 
  was 
  

   bent 
  so 
  as 
  to 
  receive 
  the 
  light 
  at 
  perpendicular 
  and 
  acute 
  

   incidence 
  in 
  the 
  two 
  cases. 
  Apparently 
  the 
  angle 
  of 
  inci- 
  

   dence 
  was 
  of 
  little 
  or 
  no 
  influence. 
  It 
  must 
  be 
  remem- 
  

   bered, 
  however, 
  that 
  the 
  aluminium 
  strip 
  was 
  scraped 
  with 
  a 
  

   knife-blade 
  and 
  was 
  far 
  from 
  having 
  a 
  polished 
  plane 
  surface. 
  

   Therefore 
  this 
  test 
  may 
  indicate 
  little 
  except 
  that 
  there 
  can 
  

   be 
  no 
  error 
  in 
  curve 
  1 
  due 
  to 
  any 
  slight 
  departure 
  of 
  the 
  shape 
  

   of 
  the 
  strip 
  from 
  its 
  supposed 
  elliptical 
  cross-section. 
  

  

  Sodium. 
  — 
  The 
  results 
  in 
  the 
  case 
  of 
  sodium 
  are 
  shown 
  in 
  

   fig. 
  6, 
  curves 
  1, 
  2, 
  3. 
  Experimental 
  difficulties 
  prevented 
  

  

  Fig. 
  6. 
  

   80 
  

  

  70 
  

   60 
  

   50 
  

  

  N 
  

  

  40 
  

  

  50 
  

  

  20 
  

  

  10 
  

   

  

  Na 
  

  

  

  

  

  

  

  

  

  UK 
  

  

  

  

  

  yS- 
  

  

  ^K 
  

  

  

  

  

  

  

  v 
  

  

  \ 
  

  

  f 
  I 
  

  

  

  

  

  J 
  

  

  \ 
  

  

  

  4^ 
  

  

  

  k 
  

  

  (lr)\ 
  

  

  > 
  

  

  x 
  '\ 
  

  

  

  

  / 
  

  

  

  

  

  

  if 
  

  

  

  \\ 
  

  

  

  

  /■ 
  

  

  

  r 
  

  

  -^ 
  i 
  

  

  

  1/ 
  

  

  c 
  

  

  \ 
  

  

  

  

  

  / 
  "©\ 
  

  

  

  

  7 
  

  

  / 
  

  

  

  \ 
  

  

  

  

  A 
  

  

  

  

  

  ys 
  

  

  

  

  

  

  

  

  ^ 
  

  

  - 
  c 
  - 
  — 
  

  

  

  

  

  

  

  50 
  60 
  10 
  SO 
  90 
  100 
  110 
  120 
  130 
  140 
  150 
  

   V 
  (10) 
  13 
  

   the 
  photoelectric 
  measurements 
  being 
  taken 
  within 
  less 
  than 
  

   one 
  hour 
  after 
  the 
  sodium 
  had 
  been 
  distilled 
  onto 
  the 
  strip 
  S. 
  

   Curves 
  1, 
  2, 
  and 
  3 
  represent 
  the 
  variation 
  of 
  N 
  with 
  v, 
  1, 
  2-J-, 
  

   and 
  18 
  hours 
  respectively 
  after 
  distillation. 
  Curve 
  4 
  repre- 
  

   sents 
  (6) 
  plotted 
  for 
  sodium, 
  the 
  ordinates 
  being 
  in 
  arbitrary 
  

   units. 
  The 
  photoelectric 
  currents 
  were 
  about 
  fifty 
  times 
  as 
  

   large 
  as 
  in 
  the 
  case 
  of 
  aluminium. 
  The 
  experimental 
  results 
  

   were 
  of 
  exactly 
  the 
  same 
  type 
  as 
  those 
  shown 
  in 
  Tables 
  III. 
  

   and 
  1Y. 
  

  

  