Bragg's Law
The mathematical condition for constructive interference of waves scattered from parallel atomic lattice planes in a crystal.
Governing formula
n λ = 2 d sin θ
SI unit
m or nm (Wavelength and Spacing)
In depth
When X-rays or matter waves of wavelength λ strike crystal planes separated by distance d at glancing angle θ, path difference between reflected waves equals 2 d sin θ. Constructive interference occurs when path difference equals an integer multiple of λ.
Examples in the real world
X-ray crystallography determining 3D molecular structures of complex proteins and DNA.