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Homework Help: Bragg X-Ray Scattering

  1. Feb 21, 2007 #1
    1. Question

    A cubic crystal of interatomic spacing of 0.24 nm is used to select
    gamma–rays of energy 100 keV from a radioactive source containing a continuum of energies. If the incident beam is normal to the crystal, at
    what angle with respect to the incident beam do the 100 keV gamma–rays appear?

    2. Equations and Variables

    Bragg's Law: n(lambda) = 2dsinx

    n is the order of intensity
    lamba is the wavelength
    d is the Bragg plane separation
    x is the angle
    E is energy, E=100keV=1.60x10^-14J

    3. Attempt

    Since the incident beam is normal to the crystal, d=0.24nm.


    = 0.0258

    x = 1.48 degrees.

    Just a bit unsure of myself. I guess it's the theory that is troubling me. I thought that the angle of incidence equals the angle of deflection. Thanks fellas.
  2. jcsd
  3. Feb 22, 2007 #2
    i think you may be confusing the fact that angle of incidence must equal to the angle of REFLECTION

    not deflection (refraction)
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