Photon Energy Calculator
A photon is a single packet of light or other electromagnetic energy. Its energy depends only on its frequency, and frequency and wavelength are linked through the speed of light. Enter either one, and this page gives the rest.
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How it works
Frequency times wavelength equals the speed of light, and photon energy equals Planck's constant times frequency. Combined, the energy in electronvolts is about 1,240 divided by the wavelength in nanometres.
The 1,240 is a constant built from the speed of light and Planck's constant, so it holds for every photon. The formula needs the wavelength in nanometres.
Worked example
A photon with a wavelength of 500 nanometres carries about 2.48 electronvolts of energy.
Questions
Why does shorter light carry more energy?
A shorter wavelength means a higher frequency. More cycles per second means more energy in each photon.
What is an electronvolt?
It is a small unit of energy, equal to what an electron gains crossing one volt. Physicists use it for photons and atoms.
Does brightness change the energy of each photon?
No. Brightness counts how many photons arrive. Each photon's energy depends only on its wavelength or frequency.
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