Wavelength

Definition

The distance between one wave crest and the next — the length of a single complete wave cycle.

$\lambda = \frac{v}{f}$

Symbol: $\lambda$ · Unit: meter (m)

Technical definition

The spatial period of a wave: the distance over which the wave's phase repeats by 2π, given by λ = v/f. It is the wave's 'length' in space, just as period is its 'length' in time.

Example

Middle C (262 Hz) traveling through air at 343 m/s has a wavelength of about 1.3 m — roughly the length of a guitar. A 5G signal at 3.5 GHz has a wavelength of only about 8.6 cm.

Common confusion

Wavelength is not amplitude. Wavelength measures how long each cycle is (horizontal spacing); amplitude measures how tall each cycle is (vertical size). A loud low note and a quiet low note can share a wavelength but have very different amplitudes — one is about pitch, the other about loudness.