Haidinger's brush

Common card · No. 295986

Haidinger's brush, more commonly known as Haidinger's brushes is an image produced by the eye, an entoptic phenomenon, first described by Austrian physicist Wilhelm Karl von Haidinger in 1844. Haidinger saw it when he looked through various minerals that polarized light. Many people are able to perceive polarization of light. Haidinger's brushes may be seen as a yellowish horizontal bar or bow-tie shape (with "fuzzy" ends, hence the name "brush") visible in the center of the visual field against the blue sky viewed while facing approximately 90° from the sun, or on any bright background. Haidinger's yellow bar is observed perpendicular to the direction of light polarization (i.e., if light polarization is vertical, then Haidinger's yellow bar is observed horizontal - like around dawn and dusk, the natural skylight maximum polarization around the north and south horizon is almost vertical as per Rayleigh sky model and so Haidinger's yellow bar is observed horizontal). The perception of this...

Read on Wikipedia · Image Daniel P. B. Smith (User:Dpbsmith), CC BY-SA 3.0