Classical Model Electrodynamics

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.