3.975642e-19
J
2.4814
eV
599,999,999,999,999.9
Hz
500
nm
3.975642e-19
J
2.4814
eV
599,999,999,999,999.9
Hz
500
nm
The Photon Energy Calculator determines the energy carried by a single photon of electromagnetic radiation from either its wavelength or frequency. Photons are the fundamental quanta of light and all electromagnetic radiation, each carrying a discrete packet of energy proportional to its frequency, as described by Planck's equation E = h*f.
Max Planck introduced the concept of energy quantization in 1900 to explain blackbody radiation, proposing that energy is exchanged only in discrete amounts, or quanta. Albert Einstein extended this in 1905 with his explanation of the photoelectric effect, for which he received the Nobel Prize: light itself consists of discrete quanta (later named photons by Gilbert Lewis in 1926), each with energy E = h*f where h is Planck's constant and f is frequency.
Since frequency and wavelength are related by c = f * lambda (where c = 3 x 10^8 m/s is the speed of light), photon energy can equivalently be written as E = h*c/lambda. Higher frequency (shorter wavelength) photons carry more energy: gamma rays and X-rays are far more energetic than visible light, which in turn exceeds infrared and radio wave photons.
The electron-volt (eV) is the most convenient unit for photon energies at the atomic and molecular scale. Visible light photons have energies of roughly 1.8 to 3.1 eV. Ultraviolet photons (3-10 eV) can break chemical bonds and damage DNA. X-ray photons (100 eV to 100 keV) can ionize atoms. Gamma ray photons (above 100 keV) can penetrate thick shielding and cause nuclear reactions.
Photon energy is central to understanding atomic spectra (photons emitted/absorbed when electrons change energy levels), photovoltaics (photons must exceed the bandgap energy to generate electron-hole pairs), photosynthesis (chlorophyll absorbs red and blue photons), laser operation, and medical imaging technologies such as PET scanning.
This calculator accepts either wavelength in nanometers or frequency in hertz and returns the photon energy in both joules and electron-volts, along with the complementary frequency or wavelength.
Photon energy is E = h*f, where h = 6.626 x 10^-34 J·s and f is frequency in Hz. If wavelength lambda is given, frequency is computed as f = c/lambda where c = 3 x 10^8 m/s. Energy in eV is obtained by dividing joules by 1.602 x 10^-19 J/eV.
Photons with energy below ~1.8 eV are infrared (not visible). Visible light spans 1.8-3.1 eV (700 nm red to 400 nm violet). UV photons above 3.1 eV can cause sunburn and photochemical reactions. X-rays range from 100 eV to 100 keV, ionizing atoms. Gamma rays above 100 keV can cause nuclear reactions.
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Green light at 550 nm has about 2.26 eV per photon. The human eye is most sensitive near this wavelength.
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A 0.1 nm X-ray photon carries about 12.4 keV, sufficient to ionize atoms and useful for crystallography.
A photon is the quantum (smallest discrete unit) of electromagnetic radiation. It is a massless particle that travels at the speed of light and carries energy E = h*f.
Planck postulated and Einstein confirmed that electromagnetic energy is quantized. Each quantum carries energy proportional to frequency, with Planck's constant h as the proportionality factor.
1 eV = 1.602 x 10^-19 J. The electron-volt is convenient for atomic/molecular energies because photon energies fall in the range of 1-10 eV, easier to work with than 10^-19 J.
No. Radio photons carry energies of nano-electronvolts to micro-electronvolts, far below the ~4-25 eV needed to ionize common atoms. Only UV, X-ray and gamma photons have sufficient energy.
Visible light spans 400-700 nm, corresponding to photon energies of roughly 1.77 eV (red, 700 nm) to 3.10 eV (violet, 400 nm).
The peak photon energy emitted by a blackbody at temperature T follows Wien's law: lambda_max = 2.898 x 10^-3 / T. The sun's surface (~5800 K) peaks in the visible range.
When photons hit a metal surface, electrons are ejected only if the photon energy exceeds the work function of the metal. Einstein's explanation of this effect established the particle nature of light.
Yes. Even though photons are massless, they carry momentum p = E/c = h/lambda. This radiation pressure is the basis of proposed solar sails for spacecraft propulsion.
A 1 mW green laser (532 nm, ~2.33 eV per photon) emits about 2.7 x 10^15 photons per second. The number is energy_per_second / energy_per_photon.
Color corresponds to wavelength (and therefore frequency and energy) of visible photons. Red has the lowest energy (~1.8 eV, 700 nm) and violet the highest (~3.1 eV, 400 nm) in the visible range.
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