As the lower half of Fig. 39.4 shows, the diffraction pattern made by electrons that pass through

Question:

As the lower half of Fig. 39.4 shows, the diffraction pattern made by electrons that pass through aluminum foil is a series of concentric rings. But if the aluminum foil is replaced by a single crystal of aluminum, only certain points on these rings appear in the pattern. Explain.

Fig. 39.4

$As the lower half of Fig. 39.4 shows, the diffraction$