﻿Transformations 
  of 
  X-Rays. 
  

  

  129 
  

  

  per 
  second 
  from 
  this 
  layer 
  iu 
  consequence 
  of 
  such 
  absorption 
  

   is, 
  as 
  we 
  have 
  seen, 
  Ikhx. 
  

  

  Therefore 
  — 
  , 
  is 
  a 
  measure 
  of 
  that 
  fraction 
  of 
  this 
  special 
  

  

  A, 
  

  

  absorption 
  of 
  energy 
  which 
  is 
  re-emitted 
  as 
  energy 
  of 
  tertiary 
  

   radiation. 
  7 
  

  

  The 
  values 
  of 
  -7 
  are 
  given 
  in 
  Table 
  VII., 
  and 
  the 
  curves 
  

  

  obtained 
  by 
  plotting 
  these 
  values 
  as 
  ordinates 
  against 
  the 
  

   values 
  of 
  Ai 
  by 
  Al 
  of 
  the 
  exciting 
  radiation 
  as 
  abscissoe 
  are 
  

   shown 
  in 
  fig. 
  5. 
  

  

  Fiff. 
  5. 
  

  

  300 
  200 
  "100 
  

  

  /9BS0RPT/0/V 
  C0EFF/C/£/vrs 
  Br 
  M. 
  

  

  For 
  any 
  given 
  tertiary 
  radiator 
  the 
  value 
  of 
  — 
  , 
  attains 
  

  

  to 
  a 
  maximum 
  for 
  a 
  value 
  of 
  Ai 
  in 
  the 
  neighbourhood 
  of 
  that 
  

   which 
  gives 
  a 
  maximum 
  value 
  of 
  k. 
  As 
  the 
  exciting 
  radia- 
  

   tion 
  becomes 
  more 
  penetrating 
  this 
  fraction 
  diminishes 
  slowly 
  

   at 
  first 
  and 
  then 
  more 
  rapidly. 
  

  

  Taking 
  the 
  case 
  of 
  copper 
  as 
  a 
  tertiary 
  radiator 
  for 
  

   example, 
  the 
  maximum 
  value 
  of 
  the 
  fraction 
  which 
  corre- 
  

   sponds 
  to 
  a 
  value 
  of 
  \ 
  about 
  89 
  is 
  nearly 
  2/5, 
  when 
  \ 
  decreases 
  

   to 
  51 
  the 
  fraction 
  has 
  fallen 
  to 
  about 
  1/4, 
  and 
  for 
  a 
  value 
  of 
  

   \, 
  = 
  6-96 
  to 
  about 
  1/40. 
  

  

  At 
  the 
  present 
  stage 
  of 
  the 
  inquiry 
  the 
  cause 
  of 
  this 
  rapid 
  

   PkiL 
  Mag. 
  S. 
  6. 
  Vol. 
  18. 
  No. 
  103. 
  JaJy 
  1909. 
  K 
  

  

  