Ewald's and von Laue's dynamical theories of X-ray diffraction

Ewald's and von Laue's dynamical theories of X-ray diffraction are discussed. Ewald derived the dispersion equations with a microscopic theory (classical electron theory), whereas von Laue used a phenomenological macroscopic approach (Maxwell's theory). As is to be expected, the dispersion equations of the two theories agree if one chooses the same physical model for the electromagnetic resonators, i.e. point dipoles or atoms.