Mechanical waves are classified based on the direction of particle movement relative to the direction of wave propagation. The primary types are:
- Transverse waves: Particles of the medium move perpendicular to the direction of the wave's travel. Examples include water surface waves and seismic S waves. These waves typically travel through solids and on the surface of liquids
- Longitudinal waves: Particles move parallel to the direction of wave propagation, characterized by compressions and rarefactions. Sound waves and seismic P waves are examples. These waves can travel through solids, liquids, and gases
- Torsional waves: These involve twisting motion around a central axis, such as vibrations in structures like bridges
Additionally, some waves, like water waves, can exhibit combined transverse and longitudinal motions, often referred to as surface waves
. Thus, mechanical waves are classified mainly as transverse, longitudinal, and torsional (or surface) waves depending on how the particles in the medium oscillate relative to the wave's direction of energy transfer. All mechanical waves require a medium (solid, liquid, or gas) to propagate because they transfer energy through particle oscillations in the medium
