Longitudinal waves
In A 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
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.
Demonstrating longitudinal waves
Longitudinal waves show areas of An area of increased pressure. In longitudinal waves, the particles in areas of compression are closer together than on average. and An 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.
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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 A material through which a wave can be transmitted (propagate)..
The Surfing GB team help demonstrate the different types of wave