Falstad's java Applet simulates ripple patterns in a shallow tank. It demonstrates interference, diffraction (single slit, double slit, etc.), refraction, resonance, and the Doppler effect.

Go through the items in the Setup menu in the upper right to get started with the Applet. The predefined setups are starting points; you can modify the sources and walls as you desire. You can draw on the screen with the mouse.

The simulation has been used to make illustrations of wave phenomena that to date the editor has not been able to photograph satisfactorily in a real tank. (For instance, the interference fringes that appear in the bright edge of shadow and in the interference pattern of a single slit.)

See Diffraction here or in the ripple tank index at right.