Q. With reference to water vapour, which of the following statements is/are correct?
1. It is a gas, the amount of which decreases with altitude.
2. Its percentage is maximum at the poles.
Select the answer using the code given below.
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
Correct answer: (a) 1 only
Question from UPSC Prelims 2024 GS Paper
Explanation:
1. “It is a gas, the amount of which decreases with altitude.”
This statement is correct. Water vapor is indeed a gas, and its concentration generally decreases as altitude increases. This is because:
– The air becomes colder at higher altitudes, and colder air can hold less water vapor.
– Most sources of water vapor (oceans, lakes, vegetation) are at or near the Earth’s surface.
– As water vapor rises, it often condenses into clouds or precipitation.
2. “Its percentage is maximum at the poles.”
This statement is incorrect. Water vapor concentration is actually lowest at the poles and highest near the equator. This is because:
– Warmer air can hold more water vapor, and the equatorial regions are warmer.
– There’s more evaporation in tropical regions due to higher temperatures and larger water bodies.
– Polar regions are cold and often covered in ice, which limits evaporation.
Therefore, the correct answer is (a) 1 only.