What is the intensity of an electromagnetic radiation?

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Discussion Overview

The discussion revolves around the computation of the intensity of electromagnetic radiation using the electric and magnetic field components. It explores definitions and calculations related to intensity, particularly in the context of Poynting flux and energy transport.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant inquires about computing intensity from the electric field components (##e_x, e_y, e_z##) and magnetic field components (##h_x, h_y, h_z##).
  • Another participant references Poynting flux as a relevant concept for understanding intensity, suggesting it relates to energy transported per unit area per unit time.
  • A subsequent post reiterates the definition of intensity as energy transported per unit area per unit time and questions if this is equivalent to the radiation received by a detector.
  • Another participant suggests that to find the energy received by a detector, one should multiply the Poynting flux by the area and the time.

Areas of Agreement / Disagreement

Participants appear to agree on the definition of intensity in terms of energy transport, but there are nuances regarding its application to detectors and the specifics of calculation methods, indicating some unresolved aspects of the discussion.

Contextual Notes

There are limitations regarding the assumptions made about the relationship between Poynting flux and intensity, as well as the conditions under which the intensity is measured or calculated.

Who May Find This Useful

This discussion may be useful for those interested in electromagnetic theory, particularly in understanding the relationship between electric and magnetic fields and their implications for intensity and energy transport in radiation.

ecastro
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How can I compute the intensity of an electromagnetic radiation if I know ##e_x, e_y, e_z, h_x, h_y,## and ##h_z##, where ##e_i## is the electric field component at ##i## and ##h_i## is the magnetic field component, also at ##i##?

Thank you in advance.
 
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jtbell said:
See the discussion of Poynting flux at about the middle of this page:

http://farside.ph.utexas.edu/teaching/em/lectures/node89.html

I assume that by "intensity" you mean energy transported by the radiation per unit area per unit time, e.g. J/(m2·s) = W/m2.
The intensity here is the amount of radiation received by a detector. Is it the same as the radiation per unit area per unit time?
 
If you want the amount of energy received by a detector that has a certain area, during a certain amount of time, then you multiply the Poynting flux (as given on that page) by the area and the time.
 

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