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Light comes in packets of energy called photons. A photon's energy depends only on its frequency: E = hf, where h is Planck's constant. Since c = fλ, this is also E = hc ÷ λ — shorter wavelengths carry more energy.
Enter a wavelength in nanometres or a frequency in hertz. The calculator gives the energy in joules and in electronvolts, the unit used in atomic physics and the photoelectric effect.
| I know the | Wavelength (nm) |
| Value | 500 |
| Photon energy (eV) | 2.47968 |
| Photon energy (J) | 3.97289e-19 |
| Frequency (Hz) | 599,585,000,000,000 |
| Wavelength (nm) | 500 |
A 500 nm photon carries 2.47968 eV (3.97289e-19 J).
Try this example →| I know the | Frequency (Hz) |
| Value | 3e18 |
| Photon energy (eV) | 12,407 |
| Photon energy (J) | 1.98782e-15 |
| Frequency (Hz) | 3e18 |
| Wavelength (nm) | 0.0999308 |
Each X-ray photon carries 12,407 eV.
Try this example →Electrons are emitted from a metal only if each photon has more energy than the metal's work function φ. The maximum kinetic energy of the emitted electrons is KE = hf − φ. This is why bright red light may emit no electrons while dim ultraviolet light does.
E = hf = hc/λ.
h = 6.62607015 × 10⁻³⁴ J·s, an exact value since 2019.
Divide by 1.602 × 10⁻¹⁹. 1 eV = 1.602 × 10⁻¹⁹ J.
Violet, because it has the shortest wavelength of visible light.