Classical Model Electrodynamics

  • Thread starter fred3142
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Hi,

I am trying to gain a better understanding of the classical model of electrodynamics, so what I mean by this is, using the idea of dipoles and electron movement to understand electrodynamics. More specifically, I'm studying plane waves, and I can't understand why when a plane wave hits a conductor, it reflects with a 180° phase shift. I 'get' why it reflects (electrons move in the conductor to oppose the incoming plane wave) but no idea why this would cause a phase shift. I thought only dipoles could cause phase shifts...

My books are filled with math and some offer limited explanations. Don't get my wrong, the maths is really helpful and certainly does neatly summarise what happens, it just doesn't offer much insight into why. I have other questions similar to the above one which I'm hoping I would be able to answer if I understood the model better. Could anyone point my to a source (book) that has actual explanations (I don't care much if it lacks maths, I have plenty of books with the maths...).

Thanks.
 

Answers and Replies

  • #2
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The simplest hand-waving explanation I know of is that a perfect conductor never has any field inside. Thus, when hit by an incident wave, its charges are re-arranged so that the incident field is exactly cancelled. That means the internal fields must by exactly in the antiphase. This field is then re-radiated (it has to be because a perfect conductor cannot absorb energy).
 

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