Editing Longitudinal wave (section)

{{Short description|Type of wave}}
{{Redirect|Pressure wave|seismic pressure waves specifically|P wave}}
[[File:Onde compression impulsion 1d 30 petit.gif|thumb|305px|alt=Graph depicting a planar wave moving left-to-right|A type of longitudinal wave: A plane pressure pulse wave.]]

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| image1 = [http://www.acs.psu.edu/drussell/Demos/waves/Lwave-v8.gif Detailed animation of longitudinal wave motion (CC-BY-NC-ND 4.0)]
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'''Longitudinal waves''' are [[wave]]s which [[Oscillation|oscillate]] in the direction which is parallel to the direction in which the wave travels and displacement of the medium is in the same (or opposite) direction of the [[wave propagation]]. [[Mechanical wave|Mechanical]] longitudinal waves are also called ''compressional'' or '''compression waves''', because they produce [[compression (physics)|compression]] and [[rarefaction]] when travelling through a medium, and '''pressure waves''', because they produce increases and decreases in [[pressure]]. A wave along the length of a stretched [[Slinky]] toy, where the distance between coils increases and decreases, is a good visualization. Real-world examples include sound waves (vibrations in pressure, a particle of displacement, and particle velocity propagated in an [[elasticity (physics)|elastic]] medium) and seismic [[P wave]]s (created by earthquakes and explosions).

The other main type of wave is the [[transverse wave]], in which the displacements of the medium are at right angles to the direction of propagation. Transverse waves, for instance, describe ''some'' bulk sound waves in [[solid]] materials (but not in [[fluid]]s); these are also called "[[Shearing (physics)|shear]] waves" to differentiate them from the (longitudinal) pressure waves that these materials also support.