What's the meaning of amplitude in EM wave?

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Discussion Overview

The discussion revolves around the meaning of amplitude in electromagnetic (EM) waves, exploring its implications in both classical and quantum contexts. Participants examine the relationship between amplitude and the electric/magnetic fields, as well as comparisons to other types of waves, such as water waves.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether amplitude refers to the displacement of photons or the magnitude of the electric/magnetic fields, suggesting a need for clarification on its meaning.
  • Another participant states that classically, the square of the amplitude of a wave is proportional to the energy density, indicating a relationship between amplitude and energy.
  • Some participants express uncertainty about the meaning of amplitude in EM waves, comparing it to water waves where amplitude relates to the variation of water molecules, and questioning what varies in EM waves.
  • A later reply asserts that in the simplest form, the amplitude of the E-field vector defines the polarization of an EM wave, providing a specific perspective on the concept.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the meaning of amplitude in EM waves, with multiple competing views and questions remaining unresolved.

Contextual Notes

Participants highlight the need for clarity regarding the definition of amplitude in the context of EM waves, noting the differences in interpretation compared to other wave types.

particle
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i learned that EM wave is varying electric field and magnetic field .But what's the meaning of the amplitude of EM wave? The displacement of the photon or the magnitude of the electric/magnetic field(no. of photons)?
 
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Classically, the square of the amplitude of a wave is proportional to the energy [density].
 


but it doesn't have its own meaning?
in water wave, the amplitude is the magnitude of the variation of water molecular.
then what's varying in the EM wave?
 
particle said:
but it doesn't have its own meaning?
in water wave, the amplitude is the magnitude of the variation of water molecular.
then what's varying in the EM wave?

In the simplest form, it's the amplitude of the E-field vector. This is what typically defines the polarization of an EM wave.

Zz.
 

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