Question

Why is a sound wave called a longitudinal wave?

Answer 1

Hint:A longitudinal wave is a wave in which the medium displaces in the same direction or the opposite direction to that of the propagation of the wave. Or say that the displacement of the is parallel to the direction of propagation. In order to answer this question, take into consideration the definition of sound wave and then relate that how the sound wave is longitudinal.

Complete answer:
Sound waves are produced due to the oscillations of pressure or say displacement of particles in a medium. These waves are generated by a vibrating object or a sound source. This vibrating object creates vibrations in the medium. As the object or the source keeps on vibrating, the vibrations keep on going and thus the vibrations (wave) propagate in a direction away from the source.

At a particular distance from the source, the pressure keeps on changing with time. The longitudinal waves are also called compressional waves because these produce compressions and rarefactions. The sound waves are also produced by compressions and rarefactions. As you can see that the sound wave is the same as a longitudinal wave.

Therefore, a sound wave is also called a longitudinal wave.

Note: The point to be noted here, is that the particles of a medium do not change the position or say that the particles do not propagate along with the wave, only the disturbances created by the source propagate through the medium. Remember that the sound wave propagates in the direction parallel to the direction of medium. Also remember that sound waves are produced due to compression and rarefaction.