Bragg law: 2d sin θ = nλ (W.L. & W.H. Bragg 1913, Nobel 1915)

W.L. Bragg & W.H. Bragg (father-and-son) 1913 Bragg law (Nobel Prize in Physics 1915): X-rays of wavelength λ incident on a crystal with lattice-plane spacing d at glancing angle θ interfere constructively when the path-length difference…