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What is the amplitude of an EM wave?

  1. Jul 19, 2013 #1
    i always hear about the frequency/wavelength, and the speed of the wave, but i never heard about the actual amplitude of the wave itself? how would one derive this? i'm not referring to intensity..... intensity deals with the number of photons being captured by a detector... i'm referring to the actual amplitude of the EM wave itself. if it truly is a wave, it MUST have an amplitude right? what is it? how do i derive it?
  2. jcsd
  3. Jul 19, 2013 #2


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    Page 11 of this link gives the relation between E-field amplitude [itex]E_0[/itex] and intensity (power per area) [itex]I[/itex] as

    [tex]I = \frac{E_0^2}{2 \ c \ \mu_0}[/tex]

    Edit added:
    The derivation comes from writing the energy density in terms of E and B (as given in any decent E-M textbook), and then using

    [tex]\text{Intensity} = \text{Energy density} \cdot c[/tex]
    Last edited: Jul 19, 2013
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