In a sound wave, particles do not come back to their original positions after hitting adjacent particles. Rather, particles in a sound wave undergo vibrational motion around their equilibrium positions.
In a medium, such as air, sound waves propagate as a result of the successive compression and rarefaction of particles. When a sound wave travels through a medium, it causes the particles in the medium to oscillate back and forth around their equilibrium positions. This oscillatory motion is what allows the sound wave to propagate through the medium.
As the sound wave passes through the medium, it compresses the air particles in certain regions, creating areas of higher pressure called compressions. These compressed regions are followed by regions of lower pressure called rarefactions, where the particles are spread out more than in their equilibrium state. This alternation of compressions and rarefactions propagates through the medium, creating a longitudinal wave.
When a particle in the medium is compressed, it moves closer to its neighboring particles, and when it reaches the maximum compression, it starts moving back towards its equilibrium position due to the restoring forces present in the medium. This motion continues until the particle reaches its maximum displacement in the opposite direction, creating a rarefaction. Again, the restoring forces bring the particle back toward its equilibrium position, and the cycle repeats as the sound wave passes through the medium.
It's important to note that while individual particles in a medium oscillate around their equilibrium positions, the overall energy and information carried by the sound wave are propagated forward. The particles themselves do not return to their original positions after interacting with adjacent particles but continue to participate in the collective motion that constitutes the sound wave.