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Wavelength, frequency and photon energy are three views of the same light. Visible light spans roughly 400 to 700 nm, which corresponds to 430 to 750 THz and photon energies near 1.8 to 3.1 electronvolts.
Frequency, wavelength and photon energy of light.
f = c / λ E = h f = h c / λ
f is frequency, c the speed of light, λ the wavelength, E the photon energy and h Planck's constant. Photon energy is per photon, not per second of illumination.
| Symbol | Meaning |
|---|---|
| f | Frequency of the light. |
| λ | Wavelength in vacuum. |
| E | Energy of a single photon. |
f = 5.45 × 10¹⁴ Hz and E = 2.25 eV. Blue light at 450 nm has a higher frequency and photon energy; red at 650 nm has less of both.
Continue with the Luminous Flux Calculator, Magnification Calculator, or the Magnifying Glass Calculator — or browse more optics and light tools and all physics calculators.
No. Frequency is set at the source. The wavelength shortens by the refractive index while the frequency stays the same.
Results are computed from the standard equations of classical mechanics. Unit conversions use the SI definitions published by NIST. Air resistance is ignored unless the calculator names a drag model.
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Content updated: September 2026