Spatial frequency
= Spatial frequency
{title2=$\nu=1/\Lambda$}
<Spatial frequency> is the number of oscillation cycles per unit length. A ripple with spatial period $\Lambda$ has <frequency> $\nu=1/\Lambda$; its angular wavenumber is $k=2\pi\nu$. In two dimensions the spatial-frequency vector specifies the orientation and period of a plane-wave pattern.