How much energy is carried by visible-light photons?

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energy levels of a luminescent centre — luminescence Figure 1: Energy levels of a luminescent centre (see text).

The energy carried by a photon of visible light is determined by its frequency and is calculated using the equation $E = h ν$ , where h is Planck’s constant and $ν$ is the frequency of the radiation. Alternatively, it can be expressed in terms of wavelength ( $λ$ ) as $E = h c / λ$ , where c is the speed of light.12

In the visible spectrum, which ranges from approximately 400 nm to 700 nm, photon energies are typically measured in electron volts (eV). These energies range from about 1.8 eV for red light to 3.1 eV for violet light. In terms of joules, the energy of a single visible-light photon is very small, on the order of $4 \times 10^{- 19}$ joules.23