Wave Number
A spatial frequency measure expressing the number of radians or wave cycles per unit distance.
Governing formula
k = 2π / λ
SI unit
rad/m (or m⁻¹)
In depth
Spatial counterpart of temporal angular frequency ω. In quantum mechanics, wavenumber is proportional to momentum ($p = hbar k$).
Examples in the real world
Expressing spatial repetition rate of laser light waves in optical spectroscopy.