History
In 1912, Friedrich and Knipping, based on work previously completed by Laue, performed the experiment described in the following figure. They bombarded a single crystal sheet of \(\ce{ZnS}\) with a polychromatic x-ray beam and placed a photographic plate behind the sample, on which they obtained:
a central spot corresponding to the transmitted beam without any change in direction
other less intense spots at more or less regular spacing around the central mark, corresponding to the diffracted beams
