Humidity, Clouds & Rainfall – NDA Geography PYQs

Question 1 [NDA 2014-II]
Which one of the following is correct regarding relative humidity?
(a) It is always expressed as a percentage
(b) It is the actual amount of water vapour present in air
(c) It is measured in grams per cubic metre
(d) It increases when temperature increases

Answer: (a) It is always expressed as a percentage
Relative humidity is the ratio of actual water vapour to maximum possible water vapour at that temperature — expressed as a percentage. Option (b) describes absolute humidity. Option (c) gives the unit for absolute humidity. Option (d) is wrong — when temperature increases, air can hold more vapour, so relative humidity actually decreases (if no vapour is added).

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Question 2 [NDA 2016-I]
Which of the following conditions favour the formation of fog?

1. Calm air
2. Clear sky
3. Low temperature near the surface
4. Presence of dust particles in the air

(a) 1 and 2 only
(b) 1, 2 and 3 only
(c) 2, 3 and 4 only
(d) 1, 2, 3 and 4

Answer: (d) 1, 2, 3 and 4
All four conditions favour fog formation. Calm air prevents mixing and allows the surface to cool. Clear sky allows maximum heat loss from the surface by radiation. Low temperature near the surface cools the air to its dew point. Dust particles act as condensation nuclei for water droplets to form around. All four together create ideal fog conditions.

Question 3 [NDA 2022-I]
A large cumulonimbus cloud is often associated with which of the following?

1. Thunderstorm
2. Violent upward air movement
3. Hail

(a) 1 only
(b) 1 and 2 only
(c) 2 and 3 only
(d) 1, 2 and 3

Answer: (d) 1, 2 and 3
Cumulonimbus clouds are the most powerful and dangerous cloud type. They are associated with all three phenomena. Violent upward air movement (strong updrafts) is what builds the cloud to its great height. Thunderstorms with lightning are a characteristic feature. Hail forms within the strong updrafts when ice particles are repeatedly carried up and down through the cloud.

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Practice Question 1 (Important for NDA)
Which of the following statements about clouds is/are correct?

1. Cirrus clouds are found at the highest altitudes.
2. Cumulonimbus clouds extend from low altitude to the tropopause.
3. Nimbostratus clouds produce drizzle while stratus clouds produce heavy continuous rain.

(a) 1 only
(b) 1 and 2 only
(c) 2 and 3 only
(d) 1, 2 and 3

Answer: (b) 1 and 2 only
Statement 1 is correct — cirrus clouds form at the highest altitudes (above 6,000 m). Statement 2 is correct — cumulonimbus extends from near the surface to the tropopause. Statement 3 is wrong — it reverses the roles. Nimbostratus produces steady, moderate to heavy continuous rain. Stratus clouds produce drizzle — not heavy rain.