While at the Brewster angle there is no reflection of the p polarization, at yet greater angles the reflection coefficient of the p polarization is always less than that of the s polarization, almost up to 90° incidence where the reflectivity of each rises towards unity. This has implications for the existence of generalized Brewster angles for dielectric metasurfaces. In the case of reflection at Brewster's angle, the reflected and refracted rays are mutually perpendicular.įor magnetic materials, Brewster's angle can exist for only one of the incident wave polarizations, as determined by the relative strengths of the dielectric permittivity and magnetic permeability. The concept of a polarizing angle can be extended to the concept of a Brewster wavenumber to cover planar interfaces between two linear bianisotropic materials. A glass plate or a stack of plates placed at Brewster's angle in a light beam can, thus, be used as a polarizer. In 1815, Brewster experimented with higher-quality materials and showed that this angle was a function of the refractive index, defining Brewster's law.īrewster's angle is often referred to as the "polarizing angle", because light that reflects from a surface at this angle is entirely polarized perpendicular to the plane of incidence (" s-polarized"). He attempted to relate the polarizing angle to the refractive index of the material, but was frustrated by the inconsistent quality of glasses available at that time. The phenomenon of light being polarized by reflection from a surface at a particular angle was first observed by Étienne-Louis Malus in 1808. Since the refractive index for a given medium changes depending on the wavelength of light, Brewster's angle will also vary with wavelength. Θ B = arctan ( n 2 n 1 ), įor a glass medium ( n 2 ≈ 1.5) in air ( n 1 ≈ 1), Brewster's angle for visible light is approximately 56°, while for an air-water interface ( n 2 ≈ 1.33), it is approximately 53°. The Fresnel equations predict that light with the p polarization ( electric field polarized in the same plane as the incident ray and the surface normal at the point of incidence) will not be reflected if the angle of incidence is The fraction that is reflected is described by the Fresnel equations, and depends on the incoming light's polarization and angle of incidence. When light encounters a boundary between two media with different refractive indices, some of it is usually reflected as shown in the figure above. This special angle of incidence is named after the Scottish physicist Sir David Brewster (1781–1868). When unpolarized light is incident at this angle, the light that is reflected from the surface is therefore perfectly polarized. Angle of incidence for which all reflected light will be polarizedĪn illustration of the polarization of light that is incident on an interface at Brewster's angle.īrewster's angle (also known as the polarization angle) is an angle of incidence at which light with a particular polarization is perfectly transmitted through a transparent dielectric surface, with no reflection.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |