^Intensity of photons
Intensity of photons is also called power density & is defined as the rate of photons (i.e. number of photons per second) crossing a given area at right angles. Mathematically intensity of photons can be expressed as,
All photons of light of a particular frequency f, or wavelength λ, have the same energy and momentum, whatever the intensity of radiation may be. By increasing the intensity of light of given wavelength, there is only an increase in the number of photons per second crossing a given area, with each photon having the same energy. In other words photon energy is independent of intensity of radiation.