What characteristic is unique to transverse waves compared to longitudinal waves?

Transverse waves exhibit a key characteristic where their oscillations occur perpendicular to the direction of energy transfer. This means that when the wave moves in a particular direction, the particles of the medium move up and down or side to side, rather than in the same direction as the wave propagation. This is distinct from longitudinal waves, where the oscillations occur parallel to the direction of energy transfer, resulting in compressions and rarefactions.

Understanding this distinction is crucial in the study of wave mechanics. For instance, in seismic waves, P-waves (a type of longitudinal wave) compress and expand the material they travel through, while S-waves (a type of transverse wave) create shear motions.

Considering the other options, the notion that transverse waves can only travel through solids but not liquids does not highlight the unique oscillation behavior that defines them. Similarly, while both types of waves require a medium to travel (therefore that is not unique), and the speed comparison can depend on various factors like the medium type, it is the nature of their oscillatory motion that fundamentally distinguishes transverse waves from longitudinal waves.