Question

How is polarisation of light obtained by scattering of light?

Answer 1

1. The light from a clear blue portion of the sky shows a rise and fall of intensity when viewed through a polaroid that is rotated.
2. This is because of sunlight, which has changed its I direction (having been scattered) on encountering the molecules of the earth’s atmosphere.
3. The electric field of light interacts with the electrons present in the air molecules.
4. Under the influence of the electric field of the incident wave the electrons in the molecules acquire components of motion in both these directions.
5. We have an observer looking at 90° to the direction of the sun. Clearly, charges accelerating parallel do not radiate energy towards this observer since their acceleration has no transverse component.
6. The radiation scattered by the molecule is therefore polarized perpendicular to the plane.
   
   Polarisation by scattering