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Question
How is polarisation of light obtained by scattering of light?
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Solution
- 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.
- This is because of sunlight, which has changed its I direction (having been scattered) on encountering the molecules of the earth’s atmosphere.
- The electric field of light interacts with the electrons present in the air molecules.
- 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 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.
- The radiation scattered by the molecule is therefore polarized perpendicular to the plane.
Polarisation by scattering
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