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What are Shock Waves and how they differ from Sound Wave?

by Harpreet_Physics

Shock Waves (SW)

Supersonic aircraft, explosions or lightning produce Shock waves. It can also produced by any other phenomena that create violent changes in pressure. SW are strong pressure waves in any elastic medium like water, solid or air.

Formation of (SW) is the result of sudden release of energy. The dissipation of mechanical, chemical, electrical and nuclear energy in a limited space will result in the formation of a shock wave. This is one of the efficient mechanisms of energy dissipation observed in nature. SW need a medium both for generation as well as for propagation because of the dissipative nature of shock waves.

How are shock waves different from sound waves?

Shock waves are different from sound waves.  In sound wave compression takes place in waves but in case of Shock waves, there exists a region in which sudden and violent change in stress, density and temperature take place. This is the reason shock waves propagate in different manner from that of ordinary acoustic waves.

Shock waves travel faster than sound waves. Also their speed increases as the amplitude increases. Whereas the intensity of a shock wave decreases faster than that of a sound wave. The reason behind this is some of the energy of the shock wave is used up to heat the medium in which it travels.

The amplitude of a strong shock wave created in air by an explosion decreases. It decreases.almost as the inverse square of the distance until the wave has become so weak that it obeys the laws of acoustic waves.

When the speed of the shock wave equals the normal speed then the shock wave dies. Also you can say shock waves reduced to an ordinary sound wave.

Properties

  • SW are nonlinear waves propagating at supersonic speeds. During earthquakes, hydraulic jumps, explosions and lightning strokes these disturbances occur in steady transonic or supersonic flows.
  • These waves are characterized as strong or weak depending upon the instantaneous changes in the properties like pressure and temperature that they bring about in the medium of propagation.
  • These waves travel faster than sound waves also their speed increases as the amplitude increases.
  • SW used to study the equation of state of any material. As these waves change the mechanical, electrical, and thermal properties of solids.
  •  As compared to the sound wave, the intensity of a shock wave decreases much faster.
  • SW need a medium both for generation as well as for propagation.
  • A shock wave carries energy and can propagate through a medium like any other ordinary wave.
  • A shock wave is characterized by a sudden discontinuity in change of pressure, temperature and density of the medium.
  • The energy and speed of a shock wave dissipates with respect to the distance.
  • Energy of the shock wave remain conserved when it passes through matter but its entropy increases.

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