Photon Energy Calculator
Energy, wavelength and frequency, from whichever you know.
Work out Photon Energy. Energy, wavelength and frequency, from whichever you know. Kelvin conversion handled for you.
Photon energy
2.4797 eV
500 nm — visible
The energy per mole is the number worth comparing against chemistry. A typical single covalent bond costs 150–500 kJ/mol to break, so visible light at roughly 240 kJ/mol can drive some photochemistry but ultraviolet at 400+ kJ/mol breaks bonds outright — that is the whole reason UV damages skin and visible light does not. Wavelength here is in vacuum; in glass or water it shortens by the refractive index while the frequency stays put.
How the Photon Energy Calculator works
Start from a wavelength, a frequency or an energy and get the other two, plus the energy per mole and the region of the spectrum it falls in. The per-mole figure is the one to compare against chemistry: it says immediately whether a photon carries enough energy to break a bond.
Also known as: wavelength to energy calculator · frequency to wavelength calculator · e=hf calculator · energy of a photon formula
Frequently asked questions
How do I convert wavelength to energy?
E = hc/λ. With h = 6.626 × 10⁻³⁴ J·s and c = 2.998 × 10⁸ m/s, a 500 nm photon carries 3.97 × 10⁻¹⁹ J, or 2.48 eV.
How much energy is in a mole of photons?
Multiply the single-photon energy by Avogadro's number. A mole of 500 nm photons — one einstein — is about 239 kJ, comparable to a weak covalent bond.
Why does ultraviolet damage skin when visible light does not?
Energy per photon. UV at 300 nm carries roughly 400 kJ/mol, enough to break C–C and C–N bonds and damage DNA directly. Visible light at 240 kJ/mol cannot, no matter how bright it is — brightness adds photons, not energy per photon.
Does wavelength change in water or glass?
Yes. The wavelength shortens by the refractive index while the frequency stays constant, so frequency is the safer quantity to quote. These figures are vacuum values.
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