Explain Polarisation by scattering.

Explanation

The light from a clear blue portion of the sky shows a rise and fall of intensity when viewed through a polaroid which is rotated. Because sunlight which has changed its direction on encountering the molecules of the earth.s atmosphere. This is called scattering. This is as shown in figurc (a).

he incident sunlight is unpolarised. The dots stand for polarisation perpendicular to the plane of the figure. The double arrows show polarisation in the plane.
Under the influence of the electric field of the incident wave the electrons in the molecules acquire components of motion in both these directions.
We have drawn an observer looking at `90^(@)` to the direction of the sun.
Here, charges accelerating parallel to the double arrows do not radiate energy towards this observer since their acceleration has no transverse component. The radiation scattered by the molecule is therefore represented by dots. It is polarised perpendicular to the plane of the figure. This explains the polarisation of scattered light from the sky.
In figure polarisation of the blue scattered light from the sky is shown.
The scattering of light by molecules was investigated by C.V. Raman and his collaborators in the 1920s. Raman was awarded the Nobel prize for physics in 1930 for this work.