Loading...
Shake a rope up and down, or push a slinky spring along its length — both produce waves, but the particles move in completely different ways relative to the direction the wave travels. That single distinction, transverse versus longitudinal, decides whether a wave can be polarised at all.
What you'll be able to do
In a , particles of the medium oscillate perpendicular to the direction the wave travels — examples include water waves, electromagnetic waves (light, radio, etc.), and waves on a string. In a , particles oscillate parallel to the direction of travel — sound waves are the classic example.
Tip — A quick way to remember: transverse = "sideways" oscillation relative to travel; longitudinal = "along the line" oscillation, in the same direction the wave moves.
In a longitudinal wave, regions where particles are pushed closer together are (higher local pressure), and regions where particles are spread further apart are (lower local pressure). A full wavelength in a longitudinal wave is the distance between two adjacent compressions (or two adjacent rarefactions).
restricts the oscillations of a transverse wave to a single plane. Because a longitudinal wave already oscillates along just one direction — the direction of travel itself — there is no additional plane to restrict, so . This is direct experimental evidence that light is a transverse wave, since light can be polarised (for instance, using polaroid sunglasses or filters).
Tip — The fact that light CAN be polarised is one of the strongest pieces of evidence that light is a transverse wave, not a longitudinal one.
Common mistakes to avoid
Key takeaways
Test yourself
Ready to lock in Longitudinal and Transverse Waves? Pick a mode and earn XP & Dobloons.