# Wave number

A number that determines the spatial periodicity of a wave (i.e., the distance required for a wave shape to repeat itself) —

\begin{align} \label{eq:12601a} k_w &= \frac {2 \pi \,f}{C} \\[0.7em]%eqn_interline_spacing &= \frac {2 \pi}{\lambda} \nonumber \end{align}

where —

 $$k_w$$ = wave number $$f$$ = frequency of oscillation $$C$$ = wave speed $$\lambda$$ = wavelength

The wave speed $$C$$ must be appropriate for the type of wave that is being evaluated. Examples:

Reference: Kinsler, p. 36