Editing Frequency (section)

== In wave propagation {{anchor|Frequency of waves}} ==
{{Further|Wave propagation}}
<!-- This section is linked from [[Hearing impairment]] -->
For periodic waves in [[Dispersion relation|nondispersive media]] (that is, media in which the wave speed is independent of frequency), frequency has an inverse relationship to the [[wavelength]], ''λ'' ([[lambda]]). Even in dispersive media, the frequency ''f'' of a [[Sine wave|sinusoidal wave]] is equal to the [[phase velocity]] ''v'' of the wave [[division (mathematics)|divided]] by the wavelength ''λ'' of the wave:
<math display=block>
f = \frac{v}{\lambda}.
</math>

In the [[special case]] of electromagnetic waves in [[vacuum]], then {{nowrap|1=''v'' = ''c''}}, where ''c'' is the [[speed of light]] in vacuum, and this expression becomes
<math display=block>
f = \frac{c}{\lambda}.
</math>

When [[monochromatic radiation|monochromatic waves]] travel from one [[medium (optics)|medium]] to another, their frequency remains the same—only their wavelength and [[phase speed|speed]] change.