Light is an electromagnetic wave produced by vibrating electric charges. It is an electromagnetic wave that has an electric and a magnetic component. Vibration causes light waves to move in more than one direction (unpolarised light), vertical and horizontal. Objects, such as filters, restrict the movement of light waves to only one direction, this process is polarisation. Polarised light may be plane-polarised, circularly-polarised or elliptical-polarised.
In 2008, Martin Schubert, a student at Rensselaer Polytechnic Institute, realised that LED lights actually produce polarised light without a filter. He then made improvements and developed the first polarised light-emitting diode (LED). The invention helps control the direction and polarisation of emitted light, allowing more light to reach a desired location. This type of lighting is suitable as backlighting for any kind of LCD screen, as it produces more colourful, vibrant and lifelike images.
Aside from LED lights, light from bulbs and the sun can produce polarised light only through a filter of some sort. Only non-metallic, flat surfaces produce a reflection that is polarised. Metal surfaces scatter a reflection, producing non-polarised light. Although a mirror is flat and glass, the backing that produces a reflection is metallic, so mirrors produce non-polarised light. Maximum polarisation occurs when light reflects off a flat surface at a 45-degree angle.
Polarised light shown onto a metallic surface will reflect polarised light. Scenes in two-dimensional movies are filmed using two cameras, each with a polarising filter that reflects light in a different direction. Played simultaneously on a screen allows the viewer, while wearing special glasses, to see both shots of the scene at the same time. Three-dimensional glasses allow the right eye to see only the image from the right camera, while allowing the left eye to see only the image from the left camera; your brain does the rest by blending the two images.
Sunglasses reduce glare by polarising the reflection from a flat surface, such as asphalt, water or ice. The reflection from a flat, horizontal surface produces a horizontal reflection. Vertically filtered sunglasses block horizontally polarised light, reducing glare.
Polaroid is a crystalline substance invented in 1939 by scientist Edwin H. Land. Polaroid has been used in camera lenses, microscopes, telescopes, sunglasses, desk lamps and windows since the 1950s and is still in existence today. In many devices, such as microscopes, two sheets of Polaroid film produce the desired image quality. The first sheet, known as a polariser, produces polarised light. The second sheet, or analyzer, determines the direction of the plane of polarised light. The axis of the analyzer must be parallel to the light vibration, or no light will pass.
- Physorg.com: Student Develops First Polarized LED
- The Physics Classroom: Polarization
- Biology Online Dictionary: Polarized Light
- Rosemount-Apple Valley-Eagan Public Schools: Honors Physics - Polarized Light
- Tulane University; Properties of Light -- Reflection, Refraction, Dispersion and Refractive Indices; Professor Stephen A. Nelson; Oct. 2002
- iCharters: Polarization PDF