The reason the energy density of an EM wave is proportional only to the amplitude squared is because electromagnetic energy density U is:
U = (E2 + B2)/2
in units where c = μ0 = ε0 = 1
The average value of E2 is proportional to Emax2, it doesn't matter how fast E is varying, so the average energy density doesn't depend on ω.
-> http://electron9.phys.utk.edu/optics421/modules/m1/production.htm [Broken]The electric field is also proportional to the acceleration of the charge. The larger the acceleration, the larger is the field.
Hmmm.... If U ∝ E2, E ∝ a and a ∝ ω, how can Uavg not be dependent on ω ?
Last edited by a moderator: