NationMaster - Encyclopedia: Brewster's angle

Brewster's angle (also known as the polarization angle) is an optical phenomenon named after the Scottish Physicist, Sir David Brewster (1781–1868). Image File history File links Illustration of brewsters angle File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Illustration of brewsters angle File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... See also list of optical topics. ... David Brewster Sir David Brewster, (December 11, 1781 – February 10, 1868) was a Scottish scientist. ... 1781 was a common year starting on Monday (see link for calendar). ... 1868 (MDCCCLXVIII) was a leap year starting on Wednesday (see link for calendar) of the Gregorian calendar or a leap year starting on Friday of the 12-day-slower Julian calendar. ...

When light moves between two media of differing refractive index, light which is p-polarized with respect to the interface will not be reflected from the interface at one particular incident angle, known as Brewster's angle, θ_B. Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye (visible light) or, in a technical or scientific context, electromagnetic radiation of wavelengths that are studied in the field of optics. ... The refractive index (or index of refraction) of a material is the factor by which the phase velocity of electromagnetic radiation is slowed in that material, relative to its velocity in a vacuum. ... In electrodynamics, polarization (also spelled polarisation) is a property of waves, such as light and other electromagnetic radiation. ... Spheres reflecting the floor and each other. ... Aviation Fig. ...

The physical mechanism for this can be qualitatively understood from the manner in which electric dipoles in the media respond to p-polarized light. One can imagine that light incident on the surface is absorbed, and then reradiated by oscillating electric dipoles at the interface between the two media. Light's polarization is always perpendicular to the direction in which the light is travelling. The dipoles that produce the transmitted (refracted) light oscillate in the polarization direction of that light. These same oscillating dipoles also generate the reflected light. However, dipoles do not radiate any energy in the direction along which they oscillate. Consequently, if the direction of the refracted light is perpendicular to the direction in which the light is predicted to be specularly reflected, the dipoles will not create any reflected light. Since, by definition, the s-polarization is parallel to the interface, the corresponding oscillating dipoles will always be able to radiate in the specular-reflection direction. This is why there is no Brewster's angle for s-polarized light. The Earths magnetic field, which is approximately a dipole. ... Diagram of specular reflection Specular reflection is the perfect, mirror-like reflection of light from a surface, in which light from a single incoming direction is reflected onto a single outgoing direction. ...

With simple trigonometry this condition can be expressed as:

$theta_1 + theta_2 = 90^circ,$

where θ₁ is the angle of incidence and θ₂ is the angle of refraction.

Using Snell's law, Snells law is the simple formula used to calculate the refraction of light when travelling between two media of differing refractive index. ...

$n_1 sin left( theta_1 right) =n_2 sin left( theta_2 right),$

we can calculate the incident angle θ₁=θ_B at which no light is reflected:

$n_1 sin left( theta_B right) =n_2 sin left( 90 - theta_B right)=n_2 cos left( theta_B right).$

Rearranging, we get:

$theta_B = arctan left( frac{n_2}{n_1} right),$

where n₁ and n₂ are the refractive indices of the two media. This equation is known as Brewster's law. The refractive index (or index of refraction) of a material is the factor by which the phase velocity of electromagnetic radiation is slowed in that material, relative to its velocity in a vacuum. ...

Note that, since all p-polarized light is refracted, any light reflected from the interface at this angle must be s-polarized. A glass plate or a stack of plates placed at Brewster's angle in a light beam can thus be used as a polarizer. A polarizer is a device that converts an unpolarized or mixed-polarization beam of electromagnetic waves (e. ...

For a glass medium (n₂≈1.5) in air (n₁≈1), Brewster's angle for visible light is approximately 56° to the normal. Since the refractive index for a given medium changes depending on the wavelength of light, Brewster's angle will also vary with wavelength.

The phenomenon of light being polarized by reflection from a surface at a particular angle was first observed by Etienne-Louis Malus in 1808. 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. In 1815, Brewster experimented with higher-quality materials and showed that this angle was a function of the refractive index, defining Brewster's law. Etienne-Louis Malus (July 23, 1775 - February 24, 1812) was a French officer, engineer, physicist, and mathematician. ...