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GeographyEasyAsked in: CDS · CDS-I 2021, GK

Ozone layer, which absorbs the ultra-violet radiation, is found in which one of the following layers of the atmosphere?

  1. A.Ionosphere
  2. B.Troposphere
  3. C.Mesosphere
  4. D.Stratosphere

Correct answer

D. Stratosphere

Explanation

The correct answer is D, Stratosphere. The ozone layer lies in the stratosphere, mostly between about 15 and 35 km above the earth, and it absorbs most of the sun's harmful ultraviolet radiation. Ozone (O3) forms when ultraviolet light splits oxygen molecules and the free oxygen atoms join other O2 molecules. By soaking up UV-B and UV-C rays, the layer protects living things from skin cancer, eye damage and harm to crops. The absorbed energy also warms the stratosphere, which is why temperature rises with height in this layer, unlike in the troposphere below. Ozone is measured in Dobson units, and its thinning by chlorofluorocarbons led to the Montreal Protocol of 1987; 16 September is World Ozone Day. Option A is wrong because the ionosphere, above about 80 km, is the layer of charged particles that reflects radio waves. Option B is wrong because the troposphere is the lowest layer, where weather occurs and temperature falls with height. Option C is wrong because the mesosphere is the coldest layer, where meteors burn up. Exam tip: ozone is in the stratosphere; weather in the troposphere; meteors in the mesosphere; radio waves in the ionosphere.

Practice Questions

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Q1.GeographyAsked in: CDS · CDS-I 2021, GKEasy

Alluvial soils vary in nature from sandy loam to clay. They are generally

  1. A.poor in potash and rich in phosphorus.
  2. B.poor in both potash and phosphorus.
  3. C.rich in both potash and phosphorus.
  4. D.rich in potash and poor in phosphorus.
Show answer
Correct answer: D. rich in potash and poor in phosphorus.

Alluvial soils, laid down by rivers, generally contain plenty of potash but lack phosphorus, and they are also often short of nitrogen and humus.

Q4.GeographyAsked in: CDS · CDS-I 2021, GKEasy

Which one of the following statements about primary waves of earthquakes is not correct ?

  1. A.They are similar to sound waves.
  2. B.They can travel only through solid materials.
  3. C.They travel through gaseous, liquid and solid materials.
  4. D.They move faster and are the first to arrive at the surface.
Show answer
Correct answer: B. They can travel only through solid materials.

This statement is false because primary waves pass through solids, liquids and gases alike. Primary or P-waves are longitudinal waves: they push and pull the rock in the same direction in which the wave travels, compressing and stretching the material just as sound waves compress air.