The wavelength of a wave is the distance it requires to complete one oscillation. In astronomy, we often refer to the wavelength of a given spectral line or other form of electromagnetic radiation (light).

Wavelength of a sine wave
Credit: Swinburne

The wavelength, λ of light is related to its frequency of oscillation, f and velocity ( c = the speed of light ) by the wave equation:

c = f λ

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