Polarisation by Selective Absorption

Selective absorption is the property of certain materials that transmit light whose electric field vibrates parallel to one particular direction (the material's own transmission axis) while absorbing essentially all light vibrating in other directions. Polaroids (polarisers) are thin, commercially manufactured sheets exploiting exactly this property, also called dichroism, to produce an intense beam of plane polarised light. Edwin Land, an American scientist, developed sheet polaroids in 1932; tourmaline is a natural polarising crystal, but polaroids are more commonly manufactured artificially, historically from tiny needle-shaped quinine iodosulphate crystals aligned with their axes parallel and packed between transparent plast …