The number of wave crests per unit distance. Wavenumber is the reciprocal of wavelength. Wavenumbers are used extensively in infrared spectroscopy, and usually have units of cm-1.
1/wavelength, the units of wavenumbers are cm, and are most commonly used as the X axis unit in infrared spectra. m = 1,000 nm = 10,000 cm m = 5,000 nm = 2,000 cm
Often 2Ï€ divided by wavelength but also may be simply reciprocal wavelength (used especially in infrared spectroscopy). According to the first definition, wavenumber is the number of waves in a distance 2Ï€ (units are those of wavelength). See amplitude.
Wavenumber in most physical sciences is a wave property inversely related to wavelength, having units of inverse length (cycles per meter). Wavenumber is the spatial analogue of frequency. Application of a Fourier transformation on data in the time domain yields a frequency spectrum; applied on data in the spatial domain (data as a function of position) yields a spectrum as a function of wavenumber.