(a) X-ray diffraction (XRD) photography for a single crystal of magnesium. (b)Schematic diagram illustrating how the spots in (a) are produced. The lead screenblocks out all beams generated from the x-ray source, except for a narrow beamtraveling in a single direction. This incident beam is diffracted by individualcrystallographic planes in the single crystal, which gives rise to the variousdiffracted beams that impinge on the photographic plate. Intersections of thesebeams with the plate appear as spots when the film is developed.