Explanations on the simulations:

• Three different zones can be obviously observed.
  • Zone I: In front of the wedge, standing waves present because of the combination of incident and reflected waves while the effect of the scattered waves is relatively weak and present as the point source waves.
  • Zone III: Behind the wedge, only scattered waves present. The wave pattern within this zone seems to be generated by a point wave source right on the tip of the wedge. But there is a radian variation of the wave amplitude. At the shadow line, the wave amplitude is as half as that of the incident waves, which is easy to understand by following Huygens' view.
  • Zone II: Besides these two zones, the incident waves dominate and the effect of the scattered waves is weak but can be observed as the parabola.
• At the shadow line, parabolas can be seen. This is the proof of our parabolic approximation.