(a) Molecules in air behave like a dipole radiator. When the sunlight falls on a molecule, dipole molecule does not scatter energy along the dipole axis, however the electric field vector of light wave vibrates just in one direction perpendicular to the direction of the propagation. The light wave having direction of electric field vector in a plane is said to be linearly polarised. In figure, a dipole molecule is lying along x-axis. Molecules behave like dipole radiators and scatter no energy along the dipole axis.
The unpolarised light travelling along x-axis strikes on the dipole molecule get scattered along y and z directions. Light traversing along y and z directions is plane polarised light.
(b) In figure unpolarised light falls on the polaroid, and transmitted light has electric vibrations in the plane consisting of polaroid axis and direction of wave propagation as shown in Fig.
If polaroid is rotated the plane of polarisation will change, however the intensity of transmitted light remain uncharged.
