Photon Energy Calculator
A 500 nm photon of green light carries 2.47968 eV, from E = hc/λ.
2.479683968664 eV
Full answer, then cut to fewer decimals (not rounded):
- 2.479683968664 eV
- 2.47968396866 eV
- 2.4796839686 eV
- 2.479683968 eV
- 2.47968396 eV
- 2.4796839 eV
- 2.479683 eV
- 2.47968 eV
- 2.4796 eV
- 2.479 eV
- 2.47 eV
- 2.4 eV
- In joules
- 3.972891714 × 10⁻¹⁹ J
- Frequency f
- 599584916000000 Hz
- Wavelength λ
- 500 nm
- Energy per mole (× Nₐ)
- 239.2531313 kJ/mol
- Region of the spectrum
- visible light
Step-by-step solution
- f = c ÷ λ = 299792458 ÷ (5 × 10⁻⁷) = 599584916000000 Hz
- E = h × f = (6.62607015 × 10⁻³⁴) × 599584916000000 = 3.972891714 × 10⁻¹⁹ J
- E = 3.972891714 × 10⁻¹⁹ ÷ (1.602176634 × 10⁻¹⁹) = 2.479683969 eV
Photon Energy Formula
E = h f = h c / λ
h = 6.62607015 × 10⁻³⁴ J·s, c = 299,792,458 m/s (both exact), f frequency, λ wavelength
Worked Example
A photon of green light with a wavelength of 500 nm:
- f = c ÷ λ = 299792458 ÷ (5 × 10⁻⁷) = 599584916000000 Hz
- E = h × f = (6.62607015 × 10⁻³⁴) × 599584916000000 = 3.972891714 × 10⁻¹⁹ J
- E = 3.972891714 × 10⁻¹⁹ ÷ (1.602176634 × 10⁻¹⁹) = 2.479683969 eV
Frequency f: 599584916000000 Hz · Wavelength λ: 500 nm · Energy per mole (× Nₐ): 239.2531313 kJ/mol · Region of the spectrum: visible light
Exact constants
Since the 2019 SI redefinition, h, c and e are fixed exactly, so photon energies from a given wavelength carry no constant uncertainty at all.
More Modern Physics Calculators
-
E = mc² Calculator
E = m c²
E energy (J), m mass (kg), c = 299,792,458 m/s exactly
Example: Converting 1 gram of mass entirely into energy: Energy E = 89875500000000 J.
-
de Broglie Wavelength Calculator
λ = h / p = h / (m v) = h / √(2 m K)
h Planck constant, p momentum, m mass, v speed, K kinetic energy (= qV after acceleration through V volts)
Example: An electron accelerated from rest through 100 V: de Broglie wavelength λ = 0.122643 nm.
-
Half-Life Calculator
N = N₀ (½)^(t / T½)
N amount left, N₀ initial amount, t elapsed time, T½ half-life; λ = ln 2 / T½
Example: 100 g of carbon-14 (half-life 5730 years) after 11,460 years: Amount remaining N = 25.
Frequently asked questions
Is there a shortcut for eV and nm?
Yes: E (eV) ≈ 1239.84 / λ (nm). Red light at 700 nm is about 1.77 eV; ultraviolet at 250 nm about 4.96 eV.
Why does photon energy matter?
It decides what light can do: only photons above a metal’s work function eject electrons (photoelectric effect), and UV photons carry enough energy to break chemical bonds in skin.
Sources
- CODATA Recommended Values of the Fundamental Physical Constants: 2018, National Institute of Standards and Technology .
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Photon Energy Calculator. Retrieved October 25, 2026, from https://scientificconverters.com/calculators/photon-energy-calculator/
IEEE
Scientific Converters, "Photon Energy Calculator," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/calculators/photon-energy-calculator/