Horizontal polarization ($|H⟩$)

Horizontal polarization is linear polarization of an electromagnetic wave with electric field along a specified horizontal transverse direction. Together with vertical polarization, it supplies a convenient pair of perpendicular basis states for a horizontally propagating beam.

An ideal horizontal polarizer transmits that component and rejects the perpendicular component. Rotating the analyzer gives the intensity variation in Malus's law. A beam with equal horizontal and vertical component intensities need not be unpolarized: their relative wave phase can instead produce diagonal linear or circular polarization. Component powers alone do not determine the full polarization state.