Sound waves are called longitudinal waves because the particles of the medium (like air) vibrate in the same direction as the wave’s movement. This means the particles move back and forth along the path the sound wave is traveling, rather than up and down or side to side.
Here’s a more detailed explanation:
Compression and Rarefaction:
Sound waves travel as a series of compressions (where the particles are close together) and rarefactions (where the particles are spread out).
Particle Vibration:
The particles of the medium vibrate back and forth as the wave passes, creating these areas of compression and rarefaction.
Parallel Movement:
The direction of this vibration is parallel to the direction the wave is traveling.
Longitudinal Definition:
This parallel vibration is the defining characteristic of a longitudinal wave.