Diffraction is the phenomenon leading to the observation of distinct maxima and minima of a wave after encountering an obstacle. It occurs in every-day-life (e.g. waves in a pond) and can be used to obtain information about matter in various states of aggregation. Especially in the solid state analysis when working with crystalline samples, diffraction methods are used to obtain proof of identity by powder diffraction on bulk samples, or investigate the molecular conformation, bond lengths and angles in the crystal structure by single crystal diffraction. Different types of radiation (X-ray, neutron and electron radiation) can be used with these techniques to give information for specific problems.

Diffraction at two slits observable as distinct maxima and minima