Oblique incidence for Electromagnetic Waves

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Discussion Overview

The discussion revolves around the representation of electric fields in diagrams for oblique incidence of electromagnetic waves. Participants explore how to choose the direction of the electric field vector in relation to the wave vector and the magnetic field vector, addressing potential inconsistencies in diagrams and the implications of oscillation.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about how to choose the direction of the electric field in diagrams for oblique incidence, noting that there seem to be two possible directions.
  • Another participant clarifies that since the electric field oscillates, either direction can be chosen as long as consistency is maintained throughout the diagram.
  • A further comment references Griffiths' book, questioning the consistency of the chosen directions of the electric fields in relation to the wave vector.
  • One participant explains that consistency should be maintained with the magnetic field vector, indicating that if the algebra results in a negative electric field, it simply means it points in the opposite direction to the assumed one.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the implications of choosing different directions for the electric field vector, as there are differing interpretations of consistency in diagrams.

Contextual Notes

There are unresolved aspects regarding the assumptions made about the directionality of the electric field and its relationship to the magnetic field vector, as well as the implications of oscillation on these choices.

barnflakes
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I'm a bit confused, when drawing the diagram for oblique incidence, how do I choose which way to draw the electric field? For example, I know the direction of the wave is in the plane of incidence and the wave vectors are simply arrows in the direction of the wave that I draw - and that the E field is polarised parallel to the plane, but that gives two directions for which I can choose E - how do I know which one? Does it just not make a difference when all is worked out in the end?
 
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Since E oscillates, you can choose either direction for the incident E arrow in your diagram, but you have to be consistent.
 
clem said:
Since E oscillates, you can choose either direction for the incident E arrow in your diagram, but you have to be consistent.

Thank you clem, however just looking at Griffiths book he has chosen two of the E fields to point to the right of the k vector and one to the left, that's not consistent?
 
I meant consistent with that you put the B vector as kXE. If the algebra gives you a negative E, that just means it points opposite to your assumed direction.
 

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