# Oblique incidence for Electromagnetic Waves

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?

## Answers and Replies

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Meir Achuz
Homework Helper
Gold Member
Since E oscillates, you can choose either direction for the incident E arrow in your diagram, but you have to be consistent.

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?

Meir Achuz
Homework Helper
Gold Member
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.