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Diffraction in crystals

  1. May 20, 2010 #1
    I read an introductory text about diffraction of X-rays in crystals and I am not sure why the wavelength in the crystal is assumed to be identical to the wavelength outside the crystal. I think that the speed of electromagnetic waves can depend on the type of matter, so wavelenghts can be different.
    Can someone explain this?
     
  2. jcsd
  3. May 21, 2010 #2
    I guess they approximate the index of refraction to be 1. I think for most materials at x-ray wavelengths it is a good approximation.
     
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