﻿Smithsonian 
  Report, 
  1929. 
  — 
  Compton 
  

  

  PLATE 
  2 
  

  

  1 
  . 
  A 
  PATTERN 
  OF 
  200 
  REGULARLY 
  SPACED 
  LINES 
  WHICH 
  WHEN 
  

   PHOTOGRAPHED 
  ONTO 
  A 
  LANTERN 
  SLIDE 
  FORMS 
  A 
  DIFFRAC- 
  

   TION 
  Grating 
  for 
  Experiments 
  on 
  Light 
  

  

  2, 
  3. 
  Diffraction 
  of 
  light 
  and 
  X 
  rays 
  

  

  , 
  The 
  upper 
  portion 
  is 
  the 
  direct 
  beam, 
  the 
  middle 
  portion 
  that 
  through 
  100 
  lines 
  to 
  the 
  inch, 
  and 
  

   the 
  lower 
  portion 
  photographed 
  through 
  a 
  grid 
  of 
  330 
  lines 
  to 
  the 
  inch. 
  3, 
  DifTraction 
  pattern 
  

   of 
  X 
  rays. 
  D 
  is 
  the 
  direct 
  beam, 
  the 
  directly 
  reflected 
  beam, 
  and 
  the 
  other 
  lines 
  are 
  due 
  to 
  dif- 
  

   fraction. 
  

  

  