Wave Motion — A/L Physics

Progressive Wave A disturbance that transfers energy from one point to another without the net transfer of the medium itself. In a progressive wave, each particle of the medium oscillates about its equilibrium position with the same amplitude and frequency, but with a phase lag that increases with distance from the source. For example, ripples spreading outward when a stone is dropped into a pond: the water molecules move up and down, but the wave pattern travels outward.

Transverse vs Longitudinal Waves In a transverse wave, particle displacement is perpendicular to the direction of wave propagation; in a longitudinal wave, particle displacement is parallel to the direction of propagation. Light and electromagnetic waves are transverse. Sound waves in air are longitudinal, where compressions (high pressure) and rarefactions (low pressure) travel through the medium. A slinky demonstrates both: shaking it sideways creates transverse waves; pushing and pulling creates longitudinal waves.