As an expert in the field of physics, particularly in wave mechanics, I can explain the concepts of compression and rarefaction in longitudinal waves. Compression is the point within a longitudinal wave where the medium's particles are at their closest proximity to each other. This is the region where the wave's energy is most concentrated, and it results in an increase in pressure and density. In other words, it's where the particles are "squeezed" together. Rarefaction, on the other hand, is the point in a longitudinal wave where the medium's particles are the furthest apart. This leads to a decrease in pressure and density, as the particles are spread out more than they are in the surrounding medium. It's the region where the particles are "stretched" apart. In summary, a compression is the point of maximum density in a longitudinal wave, while a rarefaction is the point of minimum density. read more >>

9.2 Compression and rarefaction (ESACT) However instead of crests and troughs, longitudinal waves have compressions and rarefactions. A compression is a region in a longitudinal wave where the particles are closest together. A rarefaction is a region in a longitudinal wave where the particles are furthest apart.read more >>