On this Wikipedia the language links are at the top of the page across from the article title. Bragg interference, a special case of Laue diffraction, gives the angles for coherent scattering of waves from a crystal lattice. X-rays interact with the atoms in a crystal. It was proposed that the incident X-ray radiation would produce a Bragg peak bragg’s apple cider vinegar pickles their reflections off the various planes interfered constructively.

Lawrence Bragg on 11 November 1912 to the Cambridge Philosophical Society. The concept of Bragg diffraction applies equally to neutron diffraction and electron diffraction processes. 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. When the scattered waves interfere constructively they remain in phase. Note that moving particles, including electrons, protons and neutrons, have an associated wavelength called de Broglie wavelength.

A diffraction pattern is obtained by measuring the intensity of scattered waves as a function of scattering angle. When X-rays are incident on an atom, they make the electronic cloud move, as does any electromagnetic wave. A similar process occurs upon scattering neutron waves from the nuclei or by a coherent spin interaction with an unpaired electron. Points A and C are on one plane, and B is on the plane below. There will be a path difference between the ray that gets reflected along AC’ and the ray that gets transmitted along AB, then reflected along BC. If only two planes of atoms were diffracting, as shown in the pictures, then the transition from constructive to destructive interference would be gradual as a function of angle, with gentle maxima at the Bragg angles. However, since many atomic planes are participating interference in most real materials, very sharp peaks surrounded by mostly destructive interference result.