Light Frequency ↔ Wavelength Converter
c = λν. Convert between wavelength and frequency for any electromagnetic wave.
Result
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How to use this calculator
- Pick which to compute.
- Enter the value with its unit.
- Read result with auto-formatted unit and EM band.
About this calculator
For any electromagnetic wave (radio, microwave, IR, visible, UV, X-ray), c = λν where c = 299,792,458 m/s. Visible light is 380-750 nm wavelength, equivalently 400-790 THz frequency. Red light has the longest wavelength (lowest frequency); violet has the shortest.
Frequently asked
Visible-light wavelengths?+
~380 nm (violet) to ~750 nm (red). 600 nm is yellow-orange; 532 nm green; 450 nm blue.
Why does c appear in this formula?+
Because all EM waves travel at c in vacuum. Wavelength × frequency = speed; speed is fixed at c.
Does this work in materials?+
In a medium with refractive index n, light slows to c/n. Frequency stays the same; wavelength shrinks. The calculator assumes vacuum.
Why are different units used for different bands?+
Convenience. Radio: m to mm. Microwave: cm to mm. IR: µm. Visible: nm. X-ray: pm. The calculator auto-picks.
Photon energy from frequency?+
E = hν, where h = 6.626 × 10⁻³⁴ J·s (Planck's constant). 600 THz photon = ~3.97 × 10⁻¹⁹ J = 2.48 eV.
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