This calculator finds the energy of a single photon from its frequency using the Planck relation. The Planck constant is filled in automatically; enter the frequency to get the photon's energy.
What the symbols mean
- E — photon energy (joules).
- h — Planck constant, 6.626×10⁻³⁴ J·s (auto-filled).
- ν (entered as
nu) — frequency of the light (hertz).
Worked example
Green light at about 5.5×10¹⁴ Hz has a photon energy of roughly 3.6×10⁻¹⁹ J, or about 2.3 electronvolts.
How the formula works
This is the Planck relation, one of the founding equations of quantum physics. It says light comes in discrete packets called photons, each carrying an energy set by its frequency. Higher-frequency light — bluer, then ultraviolet, then X-ray — carries more energetic photons. The Planck constant is the tiny proportionality factor linking the two.
Common mistakes to avoid
- Confusing frequency and wavelength. This formula uses frequency. If you have wavelength, first convert using speed equals wavelength times frequency.
- Unit slips. Frequency is in hertz; the answer comes out in joules. Divide by the electronvolt value to express it in eV.
Where it is used
Photon energy explains the photoelectric effect, the colours emitted by atoms, how solar cells work, and why ultraviolet and higher-energy radiation can damage living tissue while radio waves cannot.