# Frequency

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${\displaystyle \lambda ={\frac {c}{f}}\,\!}$, where c is the speed of propagation of waves in the medium, or, for electromagnetic radiation, c = 299 792 458 m/s, the speed of light.
${\displaystyle E=hf\,\!}$ , where h = 6.626 x 10-34 J•s (Planck's constant)