Photon Energy Calculator Formula
Understand the math behind the photon energy calculator. Each variable explained with a worked example.
Formulas Used
Frequency
frequency = 299792458 / (wavelength_nm * 1e-9)Energy (J)
energy_j = 6.626e-34 * 299792458 / (wavelength_nm * 1e-9)Energy (eV)
energy_ev = 6.626e-34 * 299792458 / (wavelength_nm * 1e-9) / 1.602e-19Variables
| Variable | Description | Default |
|---|---|---|
wavelength_nm | Wavelength(nm) | 550 |
How It Works
Photon Energy
A photon's energy is proportional to its frequency and inversely proportional to its wavelength.
Formula
E = h * f = h * c / lambda
where h = 6.626 x 10^-34 J·s is Planck's constant and c = 3 x 10^8 m/s. To convert to electron volts, divide by 1.602 x 10^-19.
Worked Example
A green photon with wavelength 550 nm.
- 01f = c / lambda = 3e8 / 550e-9 = 5.45e14 Hz
- 02E = h * f = 6.626e-34 * 5.45e14
- 03E = 3.614e-19 J
- 04E = 3.614e-19 / 1.602e-19 = 2.257 eV
Frequently Asked Questions
What is a photon?
A photon is a quantum (discrete packet) of electromagnetic energy. It has no mass and always travels at the speed of light.
Why do different colors have different energies?
Color corresponds to wavelength. Shorter wavelengths (violet/blue) have higher frequency and thus higher energy per photon.
What energy do X-ray photons have?
X-ray photons have energies from about 100 eV to 100 keV, much higher than visible light photons (1.8-3.1 eV).
Learn More
Guide
Understanding the Electromagnetic Spectrum
A complete guide to the electromagnetic spectrum. Learn about radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays, including their wavelengths, frequencies, and applications.
Ready to run the numbers?
Open Photon Energy Calculator