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Mihsaba›Photon Energy Calculator

Photon Energy Calculator

Calculate photon frequency and energy in joules, electronvolts and kilojoules per mole from wavelength.

Uses exact SI values for c, h, elementary charge and Avogadro constant.

How to use

Photon energy is proportional to frequency and inversely proportional to wavelength. From λ, the calculator returns ν, single-photon energy and molar photon energy.

  1. Enter λ in nm.
  2. Convert internally to meters.
  3. Calculate ν=c/λ.
  4. Calculate E=hν and display several units.

How it is calculated

ν=c/λ; E=hν=hc/λ

Example

A 550 nm photon has energy of roughly 2.25 eV.

Important notes

These conversions use vacuum c. In a medium, wavelength changes with propagation speed while frequency is set by the source.

Frequently asked questions

Why does shorter wavelength mean more energy?

Because E=hc/λ.

eV vs J?

Both are energy units; eV is convenient at atomic scales.

What is kJ/mol here?

Energy of one mole of identical photons.