Crest and Trough: The Anatomy of a Wave

The crest is the very top of a wave, its highest point above the rest position.
The trough is the lowest point of a wave, sitting below the rest position.
The vertical distance between a crest and a trough is called the wave height.
Crests and troughs are used to measure a wave’s amplitude, or energy level.
A bigger difference between crest and trough means the wave is carrying more energy.
The line halfway between crest and trough is the rest position, where the medium would be if no wave passed.
In transverse waves, particles move up at the crest and down into the trough.
Sound waves don’t have crests and troughs but use compressions and rarefactions instead.
The pattern of crests and troughs repeating gives a wave its wavelength.
From ocean waves to light waves, crests and troughs reveal the rhythm of energy in motion.