Bragg's law defines the conditions for constructive interference when X-rays scatter from a crystal lattice. Its mathematical form is: \(n\lambda = 2d \sin \theta\)
where:
$n$: An integer representing the order of diffraction.
$\lambda$: The wavelength of the X-rays.
$d$: The spacing between atomic planes in the crystal.
$\theta$: The angle of incidence (and reflection) of the X-rays with respect to the atomic planes.
Bragg's law clarifies X-ray interaction with crystals, enabling crystal structure determination. This is because the diffraction pattern depends on the atomic arrangement in the lattice.
X-ray diffraction experiments use measured diffraction angles ($\theta$) to calculate interplanar spacing ($d$), thereby deducing crystal structure from crystal plane arrangements. Although peak broadening correlates with crystallite size, Bragg's law does not provide particle size.