Photon energy and wavelength calculator

Convert between wavelength, frequency and photon energy in eV and joules.

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Uses E = hf = hc ÷ λ with the exact SI values h = 6.62607015×10⁻³⁴ J·s, c = 299,792,458 m/s and e = 1.602176634×10⁻¹⁹ C. Also reports the wavenumber 1 ÷ λ in cm⁻¹, photon momentum h ÷ λ and the conventional spectrum region (visible light is roughly 380–750 nm). Wavelengths are in vacuum, since frequency and energy stay fixed when light enters a medium.

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Worked example

A fixed demonstration, separate from the values you enter above.

I know the: Wavelength (nm)
Value in the unit shown above: 500

Example result

Wavelength: 500 nm
Frequency: 599.584916 THz
Photon energy: 2.479683969 eV
Photon energy (joules): 3.972892e-19 J
Wavenumber: 20000 cm⁻¹
Photon momentum: 1.325214e-27 kg·m/s
Spectrum region: Visible: green

E = hf = hc ÷ λ with the exact SI values h = 6.62607015×10⁻³⁴ J·s, c = 299,792,458 m/s and e = 1.602176634×10⁻¹⁹ C. Wavelengths are in vacuum; in a medium the wavelength shortens but the frequency and energy do not. Region boundaries are conventional, and visible colour names are approximate.