﻿Long-wave 
  Limits 
  of 
  the 
  Normal 
  Photoelectric 
  Effect. 
  1019 
  

  

  indicate 
  rather 
  conclusively 
  an 
  agreement 
  with 
  Einstein's 
  

   formula. 
  Indeed, 
  it 
  is 
  well 
  known 
  how 
  extremely 
  small 
  

   is 
  the 
  energy 
  of 
  the 
  radiation 
  from 
  a 
  quartz 
  lamp 
  for 
  wave- 
  

   lengths 
  less 
  than 
  A, 
  = 
  200/a/a, 
  especially 
  after 
  passage 
  through 
  

  

  Fie 
  

  

  Volt 
  

  

  a 
  quartz 
  spectroscope. 
  It 
  must 
  therefore 
  be 
  regarded 
  as 
  

   very 
  doubtful 
  whether 
  in 
  such 
  cases 
  the 
  insulation 
  losses 
  

   and 
  the 
  losses 
  due 
  to 
  charges 
  resulting 
  from 
  stray 
  light- 
  

   diffused 
  to 
  the 
  opposite 
  electrode, 
  can 
  be 
  so 
  completely 
  

   eliminated 
  that 
  the 
  illuminated 
  plate 
  actually 
  assumes 
  the 
  

   high 
  potentials 
  corresponding 
  to 
  these 
  very 
  short 
  wave- 
  

   lengths. 
  However, 
  the 
  foregoing 
  must 
  not 
  in 
  any 
  way 
  be 
  

   construed 
  as 
  a 
  criticism 
  of 
  the 
  validity 
  of 
  Einstein's 
  formula. 
  

   It 
  merely 
  seems 
  to 
  us 
  that 
  the 
  measurements 
  thus 
  far 
  made 
  in 
  

   the 
  spectral 
  region 
  between 
  185 
  /a/a 
  and 
  400 
  /a/a 
  do 
  not 
  lend 
  

   themselves 
  to 
  a 
  quantitative 
  test. 
  We 
  consider 
  that 
  at 
  

   present 
  the 
  most 
  important 
  experimental 
  support 
  for 
  Ein- 
  

   stein's 
  relation 
  is 
  the 
  fact 
  that 
  an 
  extrapolation 
  to 
  the 
  

   probable 
  frequencies 
  of 
  the 
  Rbntgen 
  spectrum 
  leads 
  to 
  velo- 
  

   cities 
  for 
  the 
  electrons 
  liberated 
  by 
  Rontgen 
  rays 
  which 
  agree 
  

   in 
  order 
  of 
  magnitude 
  with 
  those 
  experimentally 
  observed 
  *. 
  

  

  * 
  W. 
  Wien, 
  Gritting. 
  Nachr. 
  pp. 
  598-601 
  (1907) 
  ; 
  J. 
  Stark, 
  Phys. 
  Zs. 
  

   p. 
  881 
  (1907) 
  ; 
  cf. 
  R. 
  Pohl, 
  Physik 
  der 
  Rontgenstrahlen, 
  Braunschweig 
  1 
  , 
  

   1912, 
  p. 
  128. 
  

  

  3 
  Z 
  2 
  

  

  