Energy to Wavelength Calculator

Have the energy of a wave or photon, and want to find its wavelength? Look no further than the energy to wavelength calculator!

Wavelength551.0409 nm551.0409 nm — visible, around green

Photon energy2.25 eV3.605e-19 J

Frequency544.0476 THz544.047579 THz

Wavenumber18,147.4739 cm⁻¹the spectroscopist's unit — proportional to energy, which is why infrared spectra use it

Energy in kJ per mole217.092 kJ/mola mole of these photons — comparable with bond energies, which run 150 to 1000 kJ/mol

Momentum1.202e-27 kg·m/sE/c — a photon has momentum despite having no mass, which is how solar sails work

Ejects an electron from caesium?yes, with 0.15 eV to sparework function 2.1 eV — and it is the photon ENERGY that decides, not the intensity

Ejects an electron from sodium?nowork function 2.3 eV — and it is the photon ENERGY that decides, not the intensity

Ejects an electron from zinc?nowork function 4.3 eV — and it is the photon ENERGY that decides, not the intensity

Ejects an electron from platinum?nowork function 5.6 eV — and it is the photon ENERGY that decides, not the intensity

The formula

E = hf = hc ÷ λ; wavenumber = 1 ÷ λ

Energy per photon, not per beam

A photon's energy depends only on its frequency: E = hf, or equivalently hc/λ. Short wavelengths carry more energy per photon, which is why ultraviolet damages skin and infrared merely warms it — and why the brightness of a red lamp is irrelevant to whether it can cause sunburn.

That distinction is the whole content of the photoelectric effect. Whether an electron is ejected depends on the energy of each individual photon against the metal's work function; a very intense beam of low-energy photons ejects nothing at all, while a faint beam above the threshold works immediately. Classical wave theory predicts the opposite, and the failure is what established that light is quantised.

Visible light spans roughly 1.8 to 3.3 eV, which is the same order as chemical bond energies — not a coincidence, since that is exactly why molecules absorb visible light and why photosynthesis and vision are possible.

Photons carry momentum E/c despite being massless. It is tiny, but real and cumulative: solar radiation pressure perturbs spacecraft trajectories measurably and is the basis of solar sails.