This java applet is a simulation of a ripple tank. Here, it is demonstrating antireflection coating. The dark blue medium has a high refractive index; normally, this would cause waves to be reflected. But the thin layer of light blue medium has just the right refractive index and coefficient to eliminate the reflections.
Click here to view medium without coating.
Use the sliders at the lower right to adjust the simulation speed, resolution, source frequency, and brightness.
Main Ripple Tank Applet.