Apply Huygens's principle to a 5-cm-long planar wave front approaching a reflecting wall at normal incidence. The wavelength is 1 cm and the wall has a wide opening (width = 4cm). The center of the incoming wave front approaches the center of the opening. Repeat the procedure until you have wave fronts on both sides of the wall. Without worrying about the details of edge effects, what are the general shapes of the wave fronts on each side of the reflecting wall?