This page shows an interactive Java applet for supersonic flow past a wedge. The applet shows the shock wave generated by the wedge and the value of the flow variables downstream of the shock. Shock waves occur whenever an object moves faster than the speed of sound and the object abruptly constricts the flow.
Shock waves are very small regions in a gas where the gas properties change by a large amount.
Scientists call this a high gradient region, which just means a large change of variable over a very small distance. Across a shock wave, the air pressure increases almost instantaneously. The air temperature and density also increase across a shock wave, while the Mach number and speed of the flow decrease. If the shock wave is oriented perpendicular to the flow direction it is called a normal shock. If the shock wave is inclined to the flow direction it is called an oblique shock.