It is well known that when we place objects in the way of incoming monochromatic waves, whose wavelength is comparable to the size of the objects, a diffraction pattern can be observed. This phenomenon is based on the fact that the objects behave as sources of spherical waves, whose amplitudes should be summed up to yield the picture of interference, taking into account the differences in phases. A similar phenomenon can be observed during the process of scattering of X-rays and thermal neutrons from condensed matter, as their wavelength is comparable to the distance between atoms. An observable, intensity-like quantity with a dimension length squared is needed to be able to provide a mathematical formulation of the scattering process and then connect that to the structure of the liquids under study.
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