“In longitudinal waves, the vibrations are parallel to the direction of wave travel.
Examples of longitudinal waves include:
sound waves
ultrasound waves
seismic P-waves
One way to remember the movement of particles in longitudinal waves is to use the ‘P’ sound: longitudinal waves such as seismic P-waves may be thought of as pressure or push waves as the particles move parallel to the wave.
In tranverse waves, the vibrations are at right angles to the direction of wave travel.
Examples of transverse waves include:
ripples on the surface of water
vibrations in a guitar string
a Mexican wave in a sports stadium
electromagnetic waves – eg light waves, microwaves, radio waves
seismic S-waves
One way to remember the movement of particles in transverse waves is to use the ‘S’ sound: transverse waves such as seismic S-waves may be thought of as shake or shear waves as the particles move from side-to-side – crossing the direction of wave travel.”