Diffraction from Materials

Diffraction describes the perturbation of the propagation of wave motion when the wave encounters an object with different properties from the medium in which the wave is normally propagating. It is a subset of the more general phenomenon of scattering, for example the scattering of accelerated subatomic particles by nuclei that is explored by nuclear physicists or the scattering of visible light photons from surfaces of objects in a field of view into the retina of our eyes that gives us a visual impression of our surroundings. The utility of diffraction—or scattering— phenomena in general is that it is by the interaction of electromagnetic waves (like light or X-rays) or particles (like electrons or neutrons or He nuclei) that we learn about the constituents of matter and its internal organization. This is of crucial importance to a materials scientist who wishes to understand the fundamental atomic-scale origins of useful physical properties of solids (like strength, deformation and fracture, electrical conduction, magnetic response) that underlie both traditional historical uses and more modern applications in ubiquitous 21century devices. To the extent that moving particles can be considered as having wavelike properties (the “wave-particle duality” in modern physics), the two phenomena of diffraction and scattering are in essence the same and can be treated with the same formalism and with the same result.