planepolarized

Planepolarized refers to light whose electric field oscillates in a single plane perpendicular to the direction of propagation. This state is usually called plane-polarized or linearly polarized light. For a monochromatic wave, the electric field vector remains confined to a fixed plane, while the magnetic field is perpendicular to it and to the direction of travel.

Planepolarized light is typically produced by passing light through a linear polarizer, such as a polarizing filter, or by selective reflection at a surface at or near Brewster's angle. Some crystals and optical devices, including birefringent elements and polarizing beam splitters, also generate or separate plane-polarized components.

The intensity behavior of plane-polarized light upon transmission through a second polarizer (analyzer) is described by Malus's law: I_out = I_in cos^2 theta, where theta is the angle between the light's polarization direction and the axis of the analyzer. If the incident light is unpolarized, an ideal polarizer transmits half its intensity and outputs fully plane-polarized light with its polarization aligned to the polarizer’s transmission axis.

Applications include glare reduction and display technologies (LCDs and camera filters), polarimetry, and materials science such as photoelasticity, where polarized light reveals internal stresses in transparent specimens. The state of polarization can be described quantitatively by Stokes parameters or related formalisms, which also cover partially polarized or unpolarized light.