Polarised Light – UPSC Prelims

Why in News?
Indian Astronomers have found a new method to understand the atmosphere of extrasolar planets. They have shown that planets going around stars other than the Sun can be studied by observing the polarisation of light and studying polarisation signatures.
What is polarised light?
  • Light is a transverse wave. It vibrates up and down as it travels forwards. But ‘up’ and ‘down’ are not fixed directions. The vibrations could be vertical, horizontal or at any angle in between.
  • However, Polarised light is made up of waves with vibrations at only one angle.
How is light polarised?
  • Light can be polarised by passing it through a polarising filter. A polarising filter has all its molecules aligned in the same direction. As a result, only waves with vibrations aligned in the same direction can pass through.
  • Since only a small selection of the waves can pass through a polarising filter, the overall intensity of the light is reduced.
  • For example, sunglasses can be polarised to reduce brightness and glare without compromising the vision.
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