UPSC Prelims 2002·GS1·geography·climatology

Sun’s halo is produced by the refraction of light in

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  1. AWater vapour, in Stratus clouds
  2. BIce crystals in Cirrocumulus clouds
  3. CIce crystals in Cirrus cloudsCorrect
  4. DDust particles in Stratus clouds

Explanation

The correct answer is C because a sun halo is an optical phenomenon caused by the refraction of sunlight through hexagonal ice crystals. These ice crystals are found in high altitude clouds, specifically Cirrus or Cirrostratus clouds, which form at heights above 20,000 feet where temperatures are freezing. When light passes through these ice crystals, it bends at specific angles, usually creating a ring with a radius of 22 degrees around the sun. Low level clouds like Stratus clouds consist of water droplets rather than ice crystals and therefore do not produce this specific halo effect. While Cirrocumulus clouds also exist at high altitudes, they are composed of supercooled water droplets or smaller ice clumps that typically produce different phenomena like iridescence rather than the distinct 22 degree halo associated with the uniform ice crystals in Cirrus clouds.
geography: Sun’s halo is produced by the refraction of light in
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