Write any three uses of polaroids.

Hint: Polaroid is used to control the intensity of light. It is used in sun glasses, to eliminate the headlight glare in motor cars, used in photographic cameras and 3D movie cameras.

Complete step by step answer:
Polaroids are thin plastic like sheets, consisting of long chain molecules aligned in a particular direction. The electric vectors (associated with the propagating light wave) along the direction of the aligned molecules get absorbed. It transmits light only in one direction of the electric vector known as the pass axis and thereby the intensity of light decreases.

Uses of Polaroid:
1. Polaroids are used in the laboratory to produce and analyse plane polarised light.
2. Polaroids are widely used as polarizing sunglasses.
3. They are used to eliminate the headlight glare in motor
4. They are used to improve colour contrasts in old oil paintings.
5. Polaroid films are used in photographic cameras and 3D movie cameras.
6. They are used as glass windows in trains and aeroplanes to control the intensity of light.




Note: There are various methods to polarize light. For example, polarisation can be done by scattering, by reflection, by Nicol prism, by a polaroid etc. Polaroids are artificially prepared dichroic substances. Herapathite is a crystalline material made of iodo sulphate of quinine embedded on cellulose acetate parallel along the optical axis and secured between glass sheets to make polaroid.Only transverse waves can be polarised while longitudinal waves cannot be. Polaroids are used in day to day and in polarisation.