Photon Energy Calculator
Calculate the energy of a photon from its wavelength or frequency.
Shows energy in joules and electron volts, and identifies the spectral region.
Photon Energy
A photon is a quantum of electromagnetic radiation. Its energy depends on its frequency (or equivalently, its wavelength):
E = hf = hc/λ
Where:
- E = Photon energy (joules or eV)
- h = Planck’s constant = 6.62607 × 10⁻³⁴ J·s
- f = Frequency (Hz)
- c = Speed of light = 2.998 × 10⁸ m/s
- λ = Wavelength (m)
Unit conversion: 1 eV = 1.602 × 10⁻¹⁹ J
Electromagnetic spectrum reference:
| Region | Wavelength | Energy per photon |
|---|---|---|
| Radio | > 1 mm | < 0.00124 eV |
| Microwave | 1 mm – 1 m | 0.00124 – 1.24 meV |
| Infrared | 700 nm – 1 mm | 1.24 meV – 1.77 eV |
| Visible (red) | 700 nm | 1.77 eV |
| Visible (violet) | 400 nm | 3.10 eV |
| UV | 10 – 400 nm | 3.1 – 124 eV |
| X-rays | 0.01 – 10 nm | 124 eV – 124 keV |
| Gamma rays | < 0.01 nm | > 124 keV |
Photon energy is important for:
- Understanding why UV causes sunburn but visible light does not (higher photon energy can break chemical bonds)
- Solar cell design — only photons with enough energy can excite electrons
- Night vision — IR photons carry enough energy to be detected
- X-ray imaging — high-energy photons penetrate tissue