Distinguish between unpolarised and linearly polarised light

(i) Distinguish between unpolarised and linearly polarised light.
(ii) What does a polaroid consist of ? How does it produce a linearly polarised light ?
(iii) Explain briefly how sunlight is polarised by scattering through atmospheric particles

(i) In a beam of unpolarized light, the vibrations of light vectors are in all directions in a plane perpendicular to direction of propagation. In polarised light, these vibrations are only along one direction.
(ii) A polaroid consists of a long chain of molecules aligned in a particular direction. It polarises light as it allows only one component of light (electric veclors parallel to the pass-axis) to pass through it, while the other component is absorbed