Haidinger's brush

Simulated appearance of Haidinger's brush for vertically polarized light. Size and intensity exaggerated for clarity. Orientation varies with that of polarization of light source.

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.[1][2]

Many people are able to perceive polarization of light.[3] 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 away from the sun, or on any bright background. It typically occupies roughly 3–5 degrees of vision, about twice or three times the width of one's thumb held at arm's length. The direction of light polarization is perpendicular to the yellow bar (i.e., vertical if the bar is horizontal). Fainter bluish or purplish areas may be visible between the yellow brushes (see illustration). Haidinger's brush may also be seen by looking at a white area on many LCD flat panel computer screens (due to the polarization effect of the display), in which case it is often diagonal.

  1. ^ Haidinger, Wilhelm (1844). "Über das directe Erkennen des polarisirten Lichts und der Lage der Polarisationsebene" [On direct observation of polarized light and the orientation of the plane of polarization]. Annalen der Physik. 139 (9): 29–39. Bibcode:1844AnP...139...29H. doi:10.1002/andp.18441390903.
  2. ^ O'Shea, R. P.; Temple, S. E.; Misson, G. P.; Wade, N. J.; Bach, M. (2020). "Historical context, scientific context, and translation of Haidinger's (1844) discovery of naked-eye visibility of the polarization of light". arXiv:2010.15252 [physics.hist-ph].
  3. ^ O'Shea, R. P.; Misson, G. P.; Temple, S. E. (2021). "Seeing polarization of light with the naked eye". Current Biology. 31 (4): R178–R179. Bibcode:2021CBio...31.R178O. doi:10.1016/j.cub.2020.12.037. PMID 33621501. S2CID 231991919.