Energy in an electromagnetic wave

Energy in an electromagnetic wave - A more common way to...

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Energy in an electromagnetic wave The energy in an electromagnetic wave is tied up in the electric and magnetic fields. In general, the energy per unit volume in an electric field is given by: In a magnetic field, the energy per unit volume is: An electromagnetic wave has both electric and magnetic fields, so the total energy density associated with an electromagnetic wave is: It turns out that for an electromagnetic wave, the energy associated with the electric field is equal to the energy associated with the magnetic field, so the energy density can be written in terms of just one or the other: This also implies that in an electromagnetic wave, E = cB.
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Unformatted text preview: A more common way to handle the energy is to look at how much energy is carried by the wave from one place to another. A good measure of this is the intensity of the wave, which is the power that passes perpendicularly through an area divided by the area. The intensity, S, and the energy density are related by a factor of c: Generally, it's most useful to use the average power, or average intensity, of the wave. To find the average values, you have to use some average for the electric field E and the magnetic field B. The root mean square averages are used; the relationship between the peak and rms values is:...
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