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Bragg's Law




When X-rays ''hit'' an atom, they make the Electronic Cloud move as does any Electromagnetic Wave . The movement of these charges re-radiate waves with the same Frequency (blurred slightly due to a variety of effects); this phenomenon is known as the Rayleigh Scattering (or elastic scattering). These re-emitted X-rays interfere, giving constructive or destructive Interference s; this is the diffraction phenomenon.

The interference is constructive when the phase shift is proportional to 2π; this condition can be expressed by Bragg's law:

n\lambda=2d\sin( heta) \,


where
  • ''n'' is an integer,

  • λ is the Wavelength of X-rays , and moving Electrons , Protons and Neutrons ,

  • ''d'' is the spacing between the planes in the atomic lattice, and

  • θ is the angle between the incident ray and the scattering planes




''According to the 2θ deviation, the phase shift causes constructive (left figure) or destructive (right figure) interferences''

Note that moving particles, including Electrons , Protons and Neutrons , have an associated Wavelength , as determined by Louis De Broglie (see De Broglie Wavelength ).


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