Photon Energy Calculator Formula

Understand the math behind the photon energy calculator. Each variable explained with a worked example.

Use the Photon Energy Calculator

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-19

Variables

VariableDescriptionDefault
wavelength_nmWavelength(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.

wavelength_nm = 550
  1. 01f = c / lambda = 3e8 / 550e-9 = 5.45e14 Hz
  2. 02E = h * f = 6.626e-34 * 5.45e14
  3. 03E = 3.614e-19 J
  4. 04E = 3.614e-19 / 1.602e-19 = 2.257 eV

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