How are wavelength, frequency, and photon energy related?

They are linked by the equations c = lambda * nu and E = h * nu = h * c / lambda, where c is the speed of light, lambda is wavelength, nu is frequency, and h is Planck's constant. Knowing any one of wavelength, frequency, or photon energy lets you calculate the other two.

What units does the Wavelength Frequency Energy Converter support?

You can start from wavelength in nm, micrometers, meters, or angstroms, frequency in Hz up to THz, or photon energy in eV, joules, or kJ per mole. The calculator converts between all three quantities and shows results in multiple convenient units.

Does this converter work for all parts of the electromagnetic spectrum?

Yes. The underlying relations work for any photon, from radio and microwave through infrared, visible, ultraviolet, X ray, and gamma ray regions. The calculator also labels the approximate spectral region based on wavelength.

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Wavelength–Frequency–Energy Converter

Convert a photon’s wavelength, frequency, or energy and see all three side by side with steps and a mini spectrum.

Background

For a photon, the key relations are: c = λ·ν and E = h·ν = h·c / λ, where c ≈ 3.00×10⁸ m·s⁻¹ is the speed of light and h ≈ 6.63×10⁻³⁴ J·s is Planck’s constant. Knowing any one of λ, ν, or E lets you compute the other two.

Enter what you know

Known quantity

Choose whether you are starting from wavelength, frequency, or photon energy.

Wavelength

Typical visible light runs from about 380 nm to 750 nm.

Frequency

Visible light is roughly in the 400 to 800 THz range.

Photon energy

1 eV ≈ 1.602×10⁻¹⁹ J. kJ/mol is common in chemistry for photon energy.

Options:

Round to sensible significant figures

Step-by-step working

Mini spectrum: radio to gamma

Visible band and color hint

Quick picks:

Chips prefill fields and run the calculation.

Result:

No results yet. Enter a value and click Calculate.

How this calculator works

Pick what you know: wavelength, frequency, or photon energy. The tool converts everything to SI units internally.
Use core relations: we use c = λ·ν and E = h·ν = h·c / λ to find the missing quantities.
Energy units: energy can be shown in J, eV, and kJ/mol (using Avogadro’s number).
Regions of the spectrum: we classify the photon as radio, microwave, infrared, visible, ultraviolet, X ray, or gamma ray based on its wavelength.

Formula & Equations Used

Speed of light: c ≈ 3.00×10⁸ m·s⁻¹

Planck’s constant: h ≈ 6.63×10⁻³⁴ J·s

Wavelength–frequency relation: c = λ·ν, so ν = c / λ and λ = c / ν.

Photon energy: E = h·ν = h·c / λ.

Energy unit conversions: 1 eV = 1.602×10⁻¹⁹ J and E (kJ/mol) = E(J) × N_A / 1000.

Example Problems & Step-by-Step Solutions

Example 1 — 500 nm green photon

Convert 500 nm to meters: λ = 500×10⁻⁹ m = 5.00×10⁻⁷ m.
Frequency: ν = c / λ ≈ 3.00×10⁸ / 5.00×10⁻⁷ ≈ 6.00×10¹⁴ Hz.
Energy: E = h·ν ≈ 6.63×10⁻³⁴ × 6.00×10¹⁴ ≈ 4.0×10⁻¹⁹ J which is about 2.5 eV.

Example 2 — 1.0 THz microwave

Frequency: ν = 1.0 THz = 1.0×10¹² Hz.
Wavelength: λ = c / ν ≈ 3.00×10⁸ / 1.0×10¹² = 3.0×10⁻⁴ m which is 0.30 mm.
Energy: E = h·ν ≈ 6.63×10⁻³⁴ × 1.0×10¹² = 6.63×10⁻²² J, a very low energy photon.

Example 3 — 10 eV photon

Convert to joules: E = 10 eV × 1.602×10⁻¹⁹ J/eV ≈ 1.60×10⁻¹⁸ J.
Frequency: ν = E / h ≈ 1.60×10⁻¹⁸ / 6.63×10⁻³⁴ ≈ 2.4×10¹⁵ Hz.
Wavelength: λ = c / ν ≈ 3.00×10⁸ / 2.4×10¹⁵ ≈ 1.25×10⁻⁷ m which is 125 nm in the ultraviolet.