A particle (blue dot) is moving across a medium at the speed of light in that medium. Since the particle moves with the spherical wave fronts it emits, it creates a shock wave at the location of the particle.

The ratio of speeds shown above the animation is the speed of the particle divided by the speed of light in the medium, or v/c_n where c_n is the speed of light divided by the index of refraction of the medium.

Use the scroll bar to increase or decrease this ratio to see the effect.