Previous Year Question
Given below are two statements, one is labelled as Assertion (A) and the other as Reason (R).
Assertion (A): Agra and Darjeeling are located on the same latitude but temperature of January in Agra is 16°C whereas it is only 4°C in Darjeeling.
Reason (R): Temperature decreases with height and due to thin air, places in the mountains are cooler than places in the plains.
Select the correct answer from the code given below:
Both (A) and (R) are true and (R) is the correct explanation of (A)
(A) is true but (R) is false
Both (A) and (R) are true but (R) is not the correct explanation of (A)
(A) is false but (R) is true
Correct Answer: A
Detailed Solution
Agra and Darjeeling lie at approximately the same latitude, so latitude alone cannot account for such a large difference in their temperatures. The principal controlling factor here is altitude.
Agra lies at a relatively low elevation in the plains, whereas Darjeeling lies at an elevation of more than about 2,000 metres in the Himalayan mountains. With increasing altitude, atmospheric pressure and air density decrease, and temperature generally declines.
Within the troposphere, temperature generally decreases as altitude increases. Therefore, even places situated at the same or nearly the same latitude can experience very different temperatures when their elevations are substantially different.
NCERT itself gives this example—Agra and Darjiling are on the same latitude, but the January temperature is 16°C at Agra and only 4°C at Darjiling; altitude and thinner air explain the difference.
Thus, Reason (R) is not merely true independently; it provides the direct explanation for the temperature difference between Agra and Darjeeling.