In longitudinal waveA wave that moves in the same direction as the direction in which the particles are vibrating., the vibrations are parallel to the direction of wave travel.
Examples of longitudinal waves include:
sound waves
ultrasound waves
seismic P-waves
Longitudinal waves show areas of compressionAn area of increased pressure. In longitudinal waves, the particles in areas of compression are closer together than on average. and rarefactionAn area of reduced pressure. In longitudinal waves, the particles in areas of rarefaction are further apart than on average.:
compressions are regions of high pressure due to particles being close together
rarefactions are regions of low pressure due to particles being spread further apart
Longitudinal waves are often demonstrated by pushing and pulling a stretched slinky spring.
In the diagram, the compressions move from left to right and energy is transferred from left to right. However, none of the particles are transported along a longitudinal wave. Instead, they move backwards and forwards between compressions as the wave is transmitted through the mediumA material through which a wave can be transmitted (propagate)..
Transverse waves
In transverse waveA wave that moves in a direction at right angles to the way in which the particles are vibrating., 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
Transverse waves are often demonstrated by moving a rope rapidly up and down.
In the diagram the rope moves up and down, producing peaks and troughs. Energy is transferred from left to right. However, none of the particles are transported along a transverse wave. The particles move up and down as the wave is transmitted through the medium.