In which type of wave does the medium move perpendicular to the direction of the wave’s propagation?

In a transverse wave, the movement of the medium is perpendicular to the direction in which the wave travels. This means that as the wave propagates from one point to another, the particles of the medium move up and down or side to side while the wave itself moves forward. A common example of a transverse wave is seen in water waves, where water moves up and down, but the wave itself travels horizontally across the surface.

In contrast, longitudinal waves feature vibrations of the medium that occur parallel to the direction of wave propagation. Sound waves are the classic example of longitudinal waves, where areas of compression and rarefaction move along the direction of travel.

Surface waves exhibit characteristics of both transverse and longitudinal waves, occurring at the interface between two different media, such as water and air, where the motion of the medium particles is in circular patterns.

Mechanical waves require a medium to propagate, but this term encompasses both transverse and longitudinal waves; therefore, it doesn't specifically address the perpendicular motion described in the question.