A consequence of the fact that light propagates as a classical wave is the emergence of [polarized](Polarization) light beams. # Polarization direction ## S and P polarization _S_ and _P-polarization_ refers to the [polarization direction](Optical%20Polarization.md#Polarization%20direction) with respect to the [incident plane](Optics%20(Index).md#Incident%20planes) of a beam. If the polarization direction is perpendicular to the incident plane then the beam is said to be S-polarized. If it is parallel to the plane, it is said to be P-polarized. This terminology comes from the German word *senkrecht,* which translates to _perpendicular,_ and the word _parallel,_ which is the same in both German and English. ## Brewster's law #Electromagnetism/Optics/waveOptics/Polarization