# How can I calculate wavelength of a photon?

If you know the frequency of the photon, you can calculate the wavelength using the equation $\lambda = \frac{c}{\nu}$ where $c$ is the speed of light and $\nu$ is the frequency.
Example: for a photon of frequency $6 \times {10}^{12} {s}^{- 1}$ the wavelength is
$\lambda = \frac{3 \times {10}^{8} \frac{m}{s}}{6 \times {10}^{12} {s}^{- 1}} = 5 \times {10}^{- 5} m = 50 m i c r o m e t e r s$