Do electromagnetic waves lose energy as they increase their distance?

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Discussion Overview

The discussion centers around whether electromagnetic waves lose energy as they increase their distance from the source, exploring the implications of energy density and the effects of different media on wave propagation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions if there is an equation that reflects the loss of energy in electromagnetic waves as they travel further from the source.
  • Another participant argues that while the wave itself does not lose energy, the energy per unit area decreases due to the spreading of the wave as distance increases.
  • A participant raises the idea of converting electromagnetic waves into light and questions whether this conversion would conserve the wave's energy since it would no longer be spreading out.
  • It is noted that in a vacuum, the energy density of electromagnetic waves decreases inversely with the square of the distance from the source, referred to as the inverse square law, but emphasizes that energy is not actually lost.
  • Further, it is mentioned that the medium through which the electromagnetic wave travels and the frequency of the wave can affect energy loss, with some frequencies being attenuated or altered in certain media.
  • One participant points out that there is no universal equation for all electromagnetic frequencies, suggesting the use of an attenuation coefficient for specific frequency ranges instead.

Areas of Agreement / Disagreement

Participants express differing views on whether electromagnetic waves lose energy, with some asserting that energy density decreases while others emphasize that energy is not lost. The discussion remains unresolved regarding the existence of a universal equation applicable to all scenarios.

Contextual Notes

Limitations include the dependence on the medium and frequency of the electromagnetic waves, as well as the lack of a simple equation that applies universally across all frequencies.

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If electromagnetic waves loose energy as the increase their distance, is there an
equation that reflects the loss of energy?
 
Last edited:
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The wave itself does not lose energy, but since it necessarily spreads out, this will result in a smaller energy/area as the distance from the source increases.
 
Would converter the electromagnetic wave light conserve the waves energy since it is no longer spreading out?
 
It's true that as the wave spreads out the energy density decreases.
So the further the receiver is from the source the lower the available energy density is.

In a pure vacuum the energy density decreases inversely as the square of the distance from the source. This is known as the inverse square law. But none is actually lost.

But it also depends upon the medium the EM wave is traveling through and on the frequency of the EM wave itself. Some frequencies will interact with some transmission mediums and be attenuated or changed to other frequencies.

There is no simple equation, applicable to all EM frequencies, to apply. We often use an attenuation coefficient for a small range of frequencies. This has appears as a ratio not a linear relationship.
 

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