What formula does this calculator use?

Photon momentum uses p = h/λ, where h is Planck's constant (6.62607015 × 10⁻³⁴ J·s) and λ is wavelength in meters. Equivalently, p = hf/c where f is frequency and c is the speed of light.

How is photon energy related to momentum?

For a photon, E = pc = hf = hc/λ. Momentum and energy are directly proportional via E = pc, which follows from the photon's zero rest mass in special relativity.

What is an electron-volt (eV)?

An electron-volt is the energy gained by one electron moving through a 1-volt potential difference. 1 eV = 1.602176634 × 10⁻¹⁹ J. Visible light photons carry roughly 1.8–3.1 eV.

What wavelength range covers visible light?

Visible light runs from about 380 nm (violet) to 750 nm (deep red). UV light is below 380 nm; near-infrared starts above 750 nm.

Can I enter frequency instead of wavelength?

Yes. Switch the input mode to Frequency and enter the value in Hz, kHz, MHz, GHz, or THz. The calculator converts to wavelength internally using λ = c/f.

Photon Momentum Calculator

Enter a photon wavelength or frequency to instantly get its momentum, energy in joules, and energy in electron-volts.

Input

Wavelength

Visible light: 380–750 nm

Results

Enter a value above and click Calculate.

Common Photon Reference Values

Color / Type	Wavelength	Momentum (kg·m/s)	Energy (eV)

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Summary

This calculator computes photon momentum using the relation p = h/λ, where h is Planck's constant and λ is the photon wavelength. It also calculates photon energy in both joules and electron-volts (eV). You can provide either wavelength (in nanometers or meters) or frequency (in Hz through THz) as input.

How it works

Choose whether to input wavelength or frequency.
Enter the value and select the appropriate unit.
The calculator applies p = h/λ (or p = hf/c) using Planck's constant h = 6.62607015 × 10⁻³⁴ J·s.
Photon energy E = hf = hc/λ is computed simultaneously.
Energy is converted to electron-volts using 1 eV = 1.602176634 × 10⁻¹⁹ J.

Use cases

Verify photon momentum for quantum mechanics homework.
Calculate radiation pressure for optical physics problems.
Convert between wavelength, frequency, momentum, and energy for spectroscopy.
Explore the visible spectrum and UV/IR photon properties.
Validate de Broglie wavelength derivations.
Check photon energy for photoelectric effect calculations.

Frequently Asked Questions

Last updated: 2026-06-13 · Reviewed by Nham Vu