NCERT Notes: Geography- Composition of the atmosphere

Subject: Geography 
Category: The Fundamentals of Physical Geography 
Topic: NCERT Notes: Geography- Composition of the Atmosphere

NCERT notes on important topics for the UPSC civil services exam. These notes will also be useful for other competitive exams like banking PO, SSC, state civil services exams and so on. This article talks about the Composition of the atmosphere.

Composition of the atmosphere
  • The atmosphere is comprised of several gases, dust particles, and water vapour.
  • The presence of oxygen becomes insignificant at the height of 120 km from the surface of the earth with respect to the composition of the atmosphere.
  • Water vapour and Carbon dioxide occur only up to 90 km.
Ozone gas
  • Present around 10-50 km above earth surface and acts as a sieve, absorbing UV (ultraviolet rays) from the sun.
  • Ozone averts the harmful rays from reaching the surface of the earth.
Water vapour
  • Water vapour is a variable gas, declines with altitude.
  • It also drops towards the poles from the equator.
  • It acts like blanket letting the earth to neither to become too hot nor too cold.
  • It also contributes to the stability and instability in the air.
Dust particles
  • Dust particles are in higher concentration in temperate and subtropical regions due to dry winds in contrast to the Polar Regions and equatorial regions.
  • They act as hygroscopic nuclei over which water vapour of atmosphere condenses to create clouds.
Nitrogen
  • The atmosphere is composed of 78% nitrogen.
  • Nitrogen cannot be used directly from the air.
  • Biotic things need nitrogen to make proteins.
  • The Nitrogen Cycle is the way of supplying required nitrogen for living things.
Oxygen
  • The atmosphere is composed of 21% oxygen.
  • It is used by all living things and is essential for respiration.
  • It is obligatory for burning.
Argon
  • The atmosphere is composed of 0.9% argon.
  • They are mainly used in light bulbs.
Carbon Dioxide
  • The atmosphere is composed of 0.03% carbon dioxide.
  • Plants use it to make oxygen.
  • It is significant as it is opaque to outgoing terrestrial radiation and transparent to incoming solar radiation.
  • It is also blameable for the greenhouse effect.

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