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GeographyMediumAsked in: NDA · NDA-I 2021, GAT

The composition of gases in exosphere is

  1. A.Helium and Hydrogen.
  2. B.Neon and Oxygen.
  3. C.Neon and Hydrogen.
  4. D.Helium and Neon.

Correct answer

A. Helium and Hydrogen.

Explanation

The correct answer is A, Helium and Hydrogen. The exosphere, the outermost layer of the atmosphere, is made up mostly of the two lightest gases, hydrogen and helium.

Above the thermosphere, beyond roughly 500 to 600 km, the air is so thin that its atoms rarely collide with each other. Heavier gases such as nitrogen and oxygen stay at lower levels, so the few particles left this high are chiefly hydrogen and helium atoms. Some of them move fast enough to escape Earth's gravity altogether, which is why this layer slowly merges into outer space and has no sharp upper limit.

B is wrong: oxygen is a heavier gas that stays in the lower layers, and neon is only a trace gas.

C is wrong: neon is not a main gas of the exosphere, though hydrogen is.

D is wrong: helium is present, but neon is not a major gas of the exosphere.

Exam tip: layers upward are troposphere, stratosphere, mesosphere, thermosphere and exosphere, the last made of hydrogen and helium.

Practice Questions

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Q2.GeographyAsked in: CDS · CDS-II 2017, GKMedium

Which of the following statements is/are correct? 1. Himalayan rivers have their origin in the snow-covered areas, hence are dry in winter season. 2. Rivers of the Peninsular Plateau have reached maturity. 3. Himalayan rivers depict all the three stages of normal cycle of erosion. Select the correct answer using the code given below.

  1. A.2 only
  2. B.1 and 3 only
  3. C.2 and 3 only
  4. D.1, 2 and 3
Show answer
Correct answer: C. 2 and 3 only

Himalayan rivers are perennial, so statement 1 is wrong, while statements 2 and 3 are correct. Himalayan rivers such as the Ganga, Indus and Brahmaputra rise from glaciers and snowfields and also get monsoon rain, so they flow all year round, including in winter.

Q3.GeographyAsked in: CDS · CDS-II 2017, GKMedium

Which of the following statements related to latitude are true? 1. Rainfall, temperature and vegetation vary with latitude. 2. The difference between the longest day and the shortest day increases with latitude. 3. Indira Point is located approximately at 6°45' N latitude. Select the correct answer using the code given below.

  1. A.1 and 2 only
  2. B.1 and 3 only
  3. C.2 and 3 only
  4. D.1, 2 and 3
Show answer
Correct answer: D. 1, 2 and 3

All three statements about latitude are true. Latitude decides how directly the Sun's rays strike a place, so temperature, rainfall and the type of vegetation change from the equator towards the poles, from hot, wet rainforests to cold tundra.

Q4.GeographyAsked in: CDS · CDS-II 2017, GKMedium

Which of the following lakes is/are situated in Ladakh? 1. Tso Kar 2. Pangong Tso 3. Tsomgo 4. Tso Moriri Select the correct answer using the code given below.

  1. A.1 only
  2. B.2 and 3
  3. C.1, 2 and 4
  4. D.2 and 4 only
Show answer
Correct answer: C. 1, 2 and 4

Tso Kar, Pangong Tso and Tso Moriri are high-altitude lakes of Ladakh, while Tsomgo lies in Sikkim. Pangong Tso, at about 4,350 metres, is a long, narrow lake that stretches from Ladakh into Tibet, and most of its length lies on the Chinese side.