How Many Photons Are Emitted Based on Intensity and Photon Energy?

[Nopollution]

Dear all,

I have the next question: if we consider the classical definition of electromagnetic intensity it is given by [energy]/[time x surface^2]. At the same time intensity is related to the number of photons of the em radiation. So my question: given for example an intensity of 5W/[sec x cm^2] at energy Ep, how many photons at the same energy are emitted?

Thanks,
Nop

 

[Hootenanny]

Depends on the frequency of the photons. Planck's relationship will give you the energy of a single photon, divide the power by the energy of a single photon to obtain the number of photons passing through the unit area per second.