A narrow beam of electrons each of energy 200eV passes through a thin polycrystalline foil and strikes a fluorescent screen kept behind the foil. What is most likely observed on the screen?
a) A single sharp spot directly in line with the incident beam
b) A pattern of concentric bright and dark rings
c) Two bright spots symmetrically placed about the beam axis
d) A broad circular bright patch whose intensity decreases smoothly outward with no dark rings