Polarisationsfiltern

Polarisationsfilter, also known as polarizing filters, are optical filters that allow light waves oscillating in a specific direction to pass through while blocking light waves oscillating in other directions. This selective transmission is based on the principle of polarization. Light is an electromagnetic wave that oscillates in all directions perpendicular to its direction of travel. Unpolarized light, like sunlight or light from a typical lamp, has oscillations in random orientations. A polarising filter has a molecular structure that acts like a series of parallel slits. Only light waves oscillating parallel to these "slits" can pass through.

When unpolarized light encounters a polarising filter, the transmitted light becomes polarized, meaning its oscillations are now confined to a single plane. This plane is determined by the orientation of the filter's polarizing axis. If a second polarising filter, known as an analyzer, is placed behind the first, its effect depends on its orientation relative to the first filter. If the axes of the two filters are parallel, most of the light will pass through. However, if the second filter is rotated by 90 degrees (crossed polarizers), almost no light will pass through, as the oscillations allowed by the first filter are now blocked by the second.

Polarising filters have numerous applications. In photography, they are used to reduce glare from surfaces like water or glass, deepen the blue of the sky by reducing scattered light, and enhance color saturation. In sunglasses, they reduce glare for improved vision and comfort. They are also used in LCD screens to control light transmission, in scientific instruments like microscopes for examining birefringent materials, and in surveying and navigation. The transmission properties of polarising filters can be described by Malus's Law, which states that the intensity of light transmitted through a second polarizer is proportional to the square of the cosine of the angle between the polarization axes of the two filters.