Photon energy

Photon energy is the energy carried by a single photon. The energy of a photon is directly proportional to its frequency and inversely proportional to its wavelength.

  • The higher the photon’s frequency, the higher its energy. Equivalently, the shorter the photon’s wavelength, the higher its energy.
  • Photon energy is determined solely by the photon’s frequency and wavelength.
  • Other factors, such as the intensity of the radiation, do not affect the energy of individual photons. In other words, two photons of light with the same frequency have the same energy, regardless of their source. even if one was emitted from a wax candle and the other from the Sun.
  • The electronvolt (eV) and the joule are the units commonly used to express the energy of photons.
  • The energy of a photon can also be expressed:
    • In terms of its wavelength or frequency using Planck’s constant (h). E = hν = hc/λ, where E is the energy, ν is the frequency, λ is the wavelength, and c is the speed of light.
    • As a quantum of electromagnetic radiation.