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How are the wavelength and frequency of light related?

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A horizontal gradient bar displays the visible light spectrum from violet to red, labeled with corresponding frequency in terahertz, wavelength in nanometers, and photon energy in electron volts. — light When white light is spread apart by a prism or a diffraction grating, the colours of the visible spectrum appear. The colours vary according to their wavelengths. Violet has the highest frequencies and shortest wavelengths, and red has the lowest frequencies and the longest wavelengths.

In physics, the frequency ( $ν$ ) and wavelength ( $λ$ ) of light are inversely related. Because all electromagnetic waves travel at the constant speed of light ( $c$ ) in a vacuum, their relationship is defined by the equation:

$ν = \frac{c}{λ}$

In this relationship, the frequency—the number of waves passing a point per unit of time—is equal to the speed of light divided by the wavelength. Consequently, as the wavelength of light increases, its frequency decreases, and as the wavelength decreases, the frequency increases.12