Timeline for How to Measure Energy of a Electromagnetic Wave accounting also for frequency?
Current License: CC BY-SA 4.0
7 events
| when toggle format | what | by | license | comment | |
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| Nov 7, 2023 at 14:46 | comment | added | hyportnex | An apple absorbs RF energy, $D=(\epsilon +j \epsilon') E$ and dissipated power per unit volume is $p=\epsilon' E^2$, that is how microwave ovens work. The complex permittivity $\epsilon +j \epsilon'$ is frequency dependent, en.wikipedia.org/wiki/Electromagnetic_absorption_by_water with several extremely strong absorbing resonant frequencies. | |
| Nov 7, 2023 at 12:58 | comment | added | DaveTechICX44 | See my answer to this | |
| Nov 7, 2023 at 12:46 | comment | added | Ján Lalinský | Poynting energy is volume integral of the Poynting energy density, and its rate of change is proportional to frequency of the wave. The question asks about energy of EM wave, and makes an incorrect statement about the Poynting vector, which should not be taken as basis for answering. Poynting vector or its surface integral is not a measure of energy of EM wave. Volume integral of Poynting energy density is. | |
| Nov 7, 2023 at 9:44 | comment | added | hyportnex | @JanLalinsky I am not familiar with the concept you call "Poynting energy" but davetechicx44's question explicitly referred to the Poynting vector and its relationship to frequency of oscillation; see above "We know a way of measuring energy of a electromagnetic wave is the Poynting vector, which is independent of the frequency, etc." and I think my question answers that explicitly. And you may also wish to read John Rennie's "handwaving" answer above that effectively explains in words how the $S$ is directly related to that reactive power and frequency. | |
| Nov 6, 2023 at 21:37 | comment | added | Ján Lalinský | The question is about energy of wave, not about rate of change of energy of wave. Rate of change of the Poynting energy as opposed to Poynting energy does have additional $\omega$ factor, but this is not what OP asks about. | |
| Nov 6, 2023 at 21:33 | comment | added | Ján Lalinský | How is flux of complex Poynting vector phasor $\hat{S}$ relevant to the question? | |
| Nov 6, 2023 at 16:12 | history | answered | hyportnex | CC BY-SA 4.0 |