← all cardsTopic 11 · Wave Motion · Definitions
Wavefront & ray
● VERBATIM — examined word-for-wordWavefront: a line/surface joining points in phase (e.g. all crests); consecutive wavefronts one λ apart. Ray: direction of propagation, always perpendicular to wavefronts.
What this actually means
A wavefront joins points that are all at the same phase, usually all the crests. Picture the circular ridges spreading when a stone drops into a pond.
Rays are arrows showing where the energy goes, and they always cross wavefronts at right angles. Given either one, you can construct the other.
Adjacent wavefronts sit one wavelength apart, which is what lets you read λ straight off a wavefront diagram.
Prove it — watch it be true
- Watch circular fronts spread from the point source with rays drawn through them
- Check any crossing: ray meets front at 90°, everywhere
- Measure front-to-front spacing: one λ