# Normal incidence of EM wave - p & s polarization convention?

• IcedCoffee
In summary, the author seems to be unsure about what polarization is called, and the convention they use is atypical.f

#### IcedCoffee

Hi. I'm reading a paper "Transmission of light through a single rectangular hole in a real metal" and the author refers to the incident light shown below as "p-polarized" without further specification.

Note that ax > ay. Is there any convention in regarding a certain polarization as p-polarized in the case of normal incidence?

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Hmmm ... that is strange. I’ve never seen anybody use S and P to mean anything other than the relation of the electric field to the plane of incidence. They shouldn’t be defined at normal incidence.

Also, since they have a well established meaning used a million places I don’t really believe we can excuse using them some other way.

However, playing devil’s advocate, S and P come from the German words for perpendicular and parallel, so I suppose if there is something to be parallel or perpendicular to other than the plane of incidence one might use that labeling. I’d be particularly accepting of that from a German speaker.

On the other hand your diagram has the electric field perpendicular to the long axis of the rectangle and still calls it P polarized, so they get no linguistic benefit of the doubt from me. This just appears to be wrong.

Hmmm ... that is strange. I’ve never seen anybody use S and P to mean anything other than the relation of the electric field to the plane of incidence. They shouldn’t be defined at normal incidence.

Also, since they have a well established meaning used a million places I don’t really believe we can excuse using them some other way.

However, playing devil’s advocate, S and P come from the German words for perpendicular and parallel, so I suppose if there is something to be parallel or perpendicular to other than the plane of incidence one might use that labeling. I’d be particularly accepting of that from a German speaker.

On the other hand your diagram has the electric field perpendicular to the long axis of the rectangle and still calls it P polarized, so they get no linguistic benefit of the doubt from me. This just appears to be wrong.

I guess they just picked the notation rather randomly and then expected readers to figure it out from the... figure.

Also, I think what you said would make more sense, that the direction perpendicular to the slit, or whatever structure that has some sort of axis, should be called s-polarized. Thank you!