Wavenumber: Difference between revisions
imported>Johan Förberg No edit summary |
imported>Mark Widmer (Clarified that wavenumber is reciprocal of wavelength, and that wavevector (sometimes also called wavenumber) is different than wavenumber.) |
||
| Line 1: | Line 1: | ||
{{subpages}} | {{subpages}} | ||
In science, the '''wavenumber''' indicates the number of wavelengths that would fit in a unit of length. | In science, the '''wavenumber''' indicates the number of wavelengths that would fit in a unit of length, and is numerically equal to the reciprocal of the wavelength. The normal units for wavenumbers are inverse centimeters cm<sup>-1</sup>. A different name for this unit is kayser (after [[Heinrich Kayser]]). Light with a wavelength of 500 nm (green) has a wavenumber of 20,000 cm<sup>-1</sup> or 20 kK. Photon energy and frequency are proportional to wavenumber: 10 kK corresponds to 1.24 eV. | ||
Historically, wavenumbers were introduced by [[Janne Rydberg]] in the 1880's in his analyses of atomic spectra. | Historically, wavenumbers were introduced by [[Janne Rydberg]] in the 1880's in his analyses of atomic spectra. | ||
The wavevector(<math>k</math>), wavelength (<math>\lambda</math>), and frequency (<math>f</math>) are related: | |||
:<math>k = \frac{2 \pi}{\lambda}, \qquad k = \frac{2 \pi f}{v}</math> | :<math>k = \frac{2 \pi}{\lambda}, \qquad k = \frac{2 \pi f}{v},</math> | ||
where <math>v</math> is the speed of the wave. | |||
Sometimes (<math>k</math>) is also referred to as wavenumber, but is greater by a factor of <math>2 \pi</math> than the wavenumber described earlier as the reciprocal (<math>1/\lambda</math>) of the wavelength. | |||
Revision as of 22:08, 23 October 2020
In science, the wavenumber indicates the number of wavelengths that would fit in a unit of length, and is numerically equal to the reciprocal of the wavelength. The normal units for wavenumbers are inverse centimeters cm-1. A different name for this unit is kayser (after Heinrich Kayser). Light with a wavelength of 500 nm (green) has a wavenumber of 20,000 cm-1 or 20 kK. Photon energy and frequency are proportional to wavenumber: 10 kK corresponds to 1.24 eV.
Historically, wavenumbers were introduced by Janne Rydberg in the 1880's in his analyses of atomic spectra.
The wavevector(), wavelength (), and frequency () are related:
where is the speed of the wave.
Sometimes () is also referred to as wavenumber, but is greater by a factor of than the wavenumber described earlier as the reciprocal () of the wavelength.
