A Polaroid is a material which polarizes light. It consists of microcrystals of herapathite. Each crystal is a doubly refracting medium, which absorbs the ordinary ray and transmits only the extraordinary ray.
Uses of Polaroid
- Polaroids are used in the laboratory to produce and analyze plane-polarized light. Light generally scatters in all directions; but when it’s reflected from flat surfaces, it tends to become polarized. They are used in the production and analysis of plane-polarized light.
- Polaroids are widely used as polarizing sunglasses. Light creates an annoying and sometimes dangerous intensity of reflected light that causes glare and reduces visibility. Polaroids are used in sunglasses to cut off the glare reflected by horizontal surfaces.
- They are used to eliminate the headlight glare in motor cars. They are used in the glass windows of an airplane to control the intensity of light entering the airplane.
- They are used to improve color contrasts in old oil paintings.
- Polaroid films are used to produce three – dimensional moving pictures. They are used as a filter in the photographic camera.
- They are used as glass windows in trains and airplanes to control the intensity of light. In airplane one polaroid is fixed outside the window while the other is fitted inside which can be rotated. The intensity of light can be adjusted by rotating the inner polaroid.
- Aerial pictures may be taken from slightly different angles and when viewed through polaroids give a better perception of depth.
- In calculators and watches, letters and numbers are formed by liquid crystal display (LCD) through polarization of light. They are used in calculators, watches, monitors of laptops which have LCD screens.
- Polarization is also used to study the size and shape of molecules.
The modern polaroid consists of a large number of ultramicroscopic crystals of herapathite embedded with their optic axes, parallel, in a matrix of nitrocellulose. Recently, new types of Polaroid are prepared in which thin film of polyvinyl alcohol is used. These are colorless crystals that transmit more light, and give better polarization.