(adsbygoogle = window.adsbygoogle || []).push({}); The reason the energy density of an EM wave is proportional only to the amplitude squared is because electromagnetic energy density U is:

U = (E^{2}+ B^{2})/2

in units where c = μ_{0}= ε_{0}= 1

The average value of E^{2}is proportional to E_{max}^{2}, it doesn't matter how fast E is varying, so the average energy density doesn't depend on ω.

Hurkyl-> 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.... IfU ∝ E,^{2}E ∝ aanda ∝ ω, how canUnot be dependent on_{avg}ω?

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# Energy in EM wave

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