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Longitudinal wave
● VERBATIM — examined word-for-wordA wave in which the oscillations of the wave particles are parallel to the direction of propagation of the wave. Sound is THE example; has compressions and rarefactions.
What this actually means
Here the particle wobble lies along the same line as the energy travel, like a slinky pushed end-on: each coil shunts forwards and back along the slinky's own length.
Because the oscillations are parallel to propagation, the medium bunches up where neighbours converge (compressions) and thins out where they separate (rarefactions). Sound in air is the exam example every time.
Same wording trap as transverse: say oscillations parallel to the direction of propagation, never 'particles move along the wave'.
Prove it — watch it be true
- Watch the air-column particles shuffle left-right along the tube
- Watch the compression and rarefaction halos travel through them
- Oscillation parallel to travel: longitudinal