polarised

Polarised refers to the state of a wave whose oscillations occur in a particular orientation. In optics and physics, polarisation describes the direction of the electric field vector of an electromagnetic wave. Light can be unpolarised, linearly polarised, circularly polarised, or elliptically polarised, depending on how the electric field oscillates over time.

Polarisation can be produced by passing light through a polarising filter, by reflection at a dielectric interface at a suitable angle (the Brewster angle), or by scattering. It can be analysed with polarising filters and detectors. The state of polarisation is commonly described using formalisms such as Stokes parameters or Jones calculus.

In materials science, polarisation also refers to the alignment of electric dipoles in a dielectric under an applied electric field, known as dielectric polarisation. Some materials exhibit spontaneous polarisation, as in ferroelectric substances, which can lead to anisotropic optical properties (birefringence) exploited in devices like wave plates and optical modulators.

Applications span everyday and technical domains. Polarised filters reduce glare in sunglasses and photography; liquid crystal displays control light transmission through polarisation; and 3D cinema uses complementary polarisation states to separate images for each eye. In communications, polarisation multiplexing carries multiple data channels on different polarisation states, increasing bandwidth and efficiency.

The term polarised is also used metaphorically to describe a division of opinions into opposing camps. While related linguistically, social polarisation concerns ideologies and attitudes rather than the physical connotations of light polarisation.