Chapter 13. Angular wave number (13-5)

Review

The quantity \(2pi{f}\) is the angular frequency \(\omega\) of the wave (see Equations 13-1), and the combination \(2\pi/\lambda\) in Equation 13-4 is called the \(\textbf{angular wave number}\). We use the symbol \(k\) for this quantity:

Since \(2\pi\) represents the number of radians in one cycle and wavelength \(\lambda\) is in meters, the angular wave number \(k\) is measured in radians per meter (rad/m). We use the adjective \(\textit{angular}\) since the term "wave number" is typically used for \(1/\lambda\), the reciprocal of the wavelength. This quantity multiplied by \(2\pi\) is the angular wave number \(k = 2\pi{f}\).