# What is a Mach wave ?

What is a Mach wave ? How does it forms ?

An object moving in the atmosphere creates pressure disturbances. If the object is traveling less than the speed of sound, the object lies inside the pressure disturbances. If the object is moving more than the speed of sound, the object is outside of the pressure disturbances. Here, these pressure disturbances pile up behind the object. A tangent line over the piled pressure disturbances forms the Mach wave.

Mach wave makes an angle with the direction of the movement of the object called the Mach angle. Mach angle is the sine inverse of the Mach number. That is

\[Mach\,angle = {\sin ^{ – 1}}\left( {\frac{1}{M}} \right)\]

If the pressure disturbances created by the moving object are stronger than the sound wave, it will make a shock wave. Mach wave is the limiting case of an oblique shock wave.