Sound Waves — Important Questions

Perpendicular to the direction of wave propagation.

In transverse waves, the particle displacement is perpendicular to the direction of wave travel. Examples include water waves and light waves.

Parallel to the direction of wave propagation.

In longitudinal waves, the particles oscillate back and forth along the same direction as the wave travels. Sound waves in air are a common example.

Sound waves in air

Sound waves in air are longitudinal because the air molecules vibrate parallel to the direction of wave propagation, creating compressions and rarefactions.

Wavelength

Wavelength is the distance between two consecutive points in phase on a wave, such as crest to crest or trough to trough.