Another physics lesson

Waves change direction around a barrier-Diffraction!

I taught this in physics class using wave tanks, and a lake is like a giant uncontrollable wave tank.  Diffraction is why you can hear conversations from another room even if you aren't in direct line with the doorway.  And why you can still receive your radio station when you go under a bridge.  See here for an explanation.  (Scroll down past reflection, and refraction.  See here and here for examples of those.

Again, Yay physics!