Among the units commonly used to denote photon energy are the electronvolt (eV) and the joule (as well as its multiples, such as the microjoule).
The photon energy of near infrared radiation at 1 μm wavelength is approximately 1.2398 eV.
An FM radio station transmitting at 100 MHz emits photons with an energy of about 4.1357×10−7 eV.
Very-high-energy gamma rays have photon energies of 100 GeV to over 1 PeV (1011 to 1015 electronvolts) or 16 nJ to 160 μJ.
During photosynthesis, specific chlorophyll molecules absorb red-light photons at a wavelength of 700 nm in the photosystem I, corresponding to an energy of each photon of ≈ 2 eV ≈ 3×10−19 J ≈ 75 kBT, where kBT denotes the thermal energy.
A minimum of 48 photons is needed for the synthesis of a single glucose molecule from CO2 and water (chemical potential difference 5×10−18 J) with a maximal energy conversion efficiency of 35%.