Photon Energy Calculator

What Is Photon Energy?

Light travels as waves, but energy is carried in discrete packets called photons. Each photon has a fixed energy set by its frequency or wavelength. Shorter wavelengths mean higher energy per photon.

Planck's Equation

Photon energy can be written two equivalent ways:

$$E = hf = \frac{hc}{\lambda}$$

where:

$h = 6.626 \times 10^{-34}\,\text{J·s}$ — Planck constant
$f$ — frequency (Hz)
$\lambda$ — wavelength (m)
$c = 2.998 \times 10^8\,\text{m/s}$ — speed of light

For visible light, electronvolts are convenient. Green light near 520 nm has energy about 2.38 eV.

Frequently Asked Questions

Which photons are most energetic?

Shorter wavelengths carry more energy. Gamma rays are the most energetic photons in the electromagnetic spectrum.

What is the energy of 450 nm blue light?

About 2.75 eV. Divide Planck energy by the electron charge to convert joules to electronvolts.

How do I convert wavelength to frequency?

Divide the speed of light by the wavelength in meters. For 520 nm, frequency is about 577 THz.

Why is photon energy so small in joules?

Planck's constant is tiny. A single visible photon carries only about 10⁻¹⁹ joules, which is why we use eV for atomic-scale work.

Does photon energy depend on brightness?

No. Brightness changes photon count, not individual photon energy. Energy depends only on frequency or wavelength.

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What Is Photon Energy?

Planck's Equation

Frequently Asked Questions

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