1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Definition of Intensity

  1. Jul 3, 2006 #1
    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?

  2. jcsd
  3. Jul 3, 2006 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    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.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Definition of Intensity
  1. Definition of (Replies: 1)

  2. Intensity of waves (Replies: 28)