Photon Energy Calculator

How it works

1. 1Select whether you know the photon’s wavelength (in nanometres) or its frequency (in hertz).
2. 2Enter the value. Wavelength converts nm → metres (× 1×10⁻⁹) then applies E = h·c ÷ λ; frequency applies E = h·f, with h = 6.626×10⁻³⁴ J·s.
3. 3The result is shown in joules (J) and electronvolts (eV), so you can compare against the visible-light range of ≈ 1.6–3.3 eV.

Use cases

• Physics students verifying photoelectric-effect or Bohr-model homework.
• Optical engineers checking the photon energy of a laser line or LED band.
• Chemistry researchers comparing bond energies (eV) against UV or visible photon energies.

Frequently asked questions

What formulas does the calculator use?

For frequency: E = h·f, with h = 6.626×10⁻³⁴ J·s and f in hertz. For wavelength: E = h·c ÷ λ, with c = 2.998×10⁸ m/s and λ converted from nm to metres (× 10⁻⁹). The eV result uses 1 eV = 1.602×10⁻¹⁹ J.

Can you show a worked example?

A green photon at λ = 500 nm = 5×10⁻⁷ m: E = (6.626×10⁻³⁴ × 2.998×10⁸) ÷ 5×10⁻⁷ ≈ 3.97×10⁻¹⁹ J ≈ 2.48 eV — inside the visible range of 1.6–3.3 eV.

Why is photon energy expressed in electronvolts?

A single photon’s energy is tiny in joules (~10⁻¹⁹ J). The electronvolt is a natural atomic-scale unit: 1 eV ≈ 1.602×10⁻¹⁹ J, so visible photons fall in the convenient 1.6–3.3 eV range, directly comparable to band gaps and bond energies.