Editing Wavenumber (section)

====Unit conversions====
The frequency of light with wavenumber <math>\tilde{\nu}</math> is
: <math>f = \frac{c}{\lambda} = c \tilde{\nu}</math>,
where <math>c</math> is the [[speed of light]].
The conversion from spectroscopic wavenumber to frequency is therefore<ref>{{cite web |url= http://www.britannica.com/EBchecked/topic/637882/wave-number
|title= Wave number|author=<!--Staff writer(s); no by-line.--> |website= [[Encyclopædia Britannica]]|access-date= 19 April 2015}}</ref>

: <math>1~\mathrm{cm}^{-1}  :=29.979245~\mathrm{GHz}. </math>

Wavenumber can also be used as [[unit of energy]], since a photon of frequency <math>f</math> has energy <math>hf</math>, where <math>h</math> is [[Planck's constant]].
The energy of a photon with wavenumber <math> \tilde{\nu} </math> is
: <math>E = hf = hc \tilde{\nu}</math>.
The conversion from spectroscopic wavenumber to energy is therefore
: <math>1~\mathrm{cm}^{-1} 
:= 1.986446 \times 10^{-23}~\mathrm{J}
= 1.239842 \times 10^{-4}~\mathrm{eV}
</math>
where energy is expressed either in [[Joule|J]] or 
[[Electronvolt|eV]].