What do "rarefactions" refer to in longitudinal waves?

In longitudinal waves, "rarefactions" refer to regions of low pressure. This phenomenon occurs when the particles of the medium are spread apart, resulting in a decrease in pressure as the wave travels through the medium. In a longitudinal wave, such as a sound wave, areas of compression (where particles are close together and pressure is high) alternate with areas of rarefaction, leading to the characteristic oscillatory motion of the wave. The low pressure in rarefactions is crucial in the propagation of the wave, as it allows for the movement of energy through the medium. Thus, understanding rarefaction is essential for grasping the behavior and features of longitudinal waves.