Bragg's law
![X-rays interact with the atoms in a crystal.](/Images/godic/202501/01/Diffusion_rayleigh_et_diffraction_svg.svg5216.png")
![According to the 2θ deviation, the phase shift causes constructive (left figure) or destructive (right figure) interferences.](/Images/godic/202501/01/Braggs_Law.svg5217.png")
![Bragg diffraction. Two beams with identical wavelength and phase approach a crystalline solid and are scattered off two different atoms within it. The lower beam traverses an extra length of 2dsinθ. Constructive interference occurs when this length is equal to an integer multiple of the wavelength of the radiation.](/Images/godic/202501/01/BraggPlaneDiffraction.svg5217.png")
![](/Images/godic/202501/01/Bragg's_law.svg5217.png")
In physics, Bragg's Law (or "Wulff-Bragg's condition" in post-Soviet countries, a special case of Laue diffraction) gives the angles for coherent and incoherent scattering from a crystal lattice. When X-rays are incident on an atom, they make the electronic cloud move as does any electromagnetic wave. The movement of these charges re-radiates waves with the same frequency, blurred slightly due to a variety of effects; this phenomenon is known as Rayleigh scattering (or elastic scattering). The scattered waves can themselves be scattered but this secondary scattering is assumed to be negligible.