Std. 8 Geography | Chapter 3 – Humidity and Clouds

Maharashtra Board Textbook Solutions
Standard VIII Geography
Chapter 3 – Humidity and Clouds

Q.1 Match the columns and complete the chain.

Ans:
A B C
Cirrus Higher altitude Floating clouds
Cumulonimbus Vertical extent in the sky Roaring clouds
Nimbostratus Low altitude Continuous rainfall
Alto-cumulus Medium altitude Snowflake clouds

Q.2 Choose the correct word from the brackets and complete the sentences.

Ans:
  • (a) The vapour-holding capacity of air depends on its temperature.
  • (b) The amount of vapour in 1 cu.m. of air shows the absolute humidity.
  • (c) As relative humidity is low in desert areas, the air remains dry.
  • (d) Cumulonimbus clouds are indicators of storms.
  • (e) In a free environment, condensation of water vapour takes place around dust particles.

Q.3 Differentiate between

(a) Humidity and Clouds

Humidity Clouds
Humidity is the amount of water vapour present in the atmosphere. Clouds are visible masses of tiny water droplets or ice crystals formed in the atmosphere.
Humidity determines whether the air is dry or moist. Clouds are formed due to condensation.
Humidity is of two types – Absolute Humidity and Relative Humidity. Clouds are classified as High, Medium, Low and Cumulonimbus clouds.

(b) Relative Humidity and Absolute Humidity

Relative Humidity Absolute Humidity
It is the percentage of water vapour present compared to the vapour-holding capacity of air. It is the actual amount of water vapour present in 1 cubic metre of air.
It changes with temperature and location. It depends mainly on the amount of moisture in the air.
It is expressed in percentage (%). It is expressed in grams per cubic metre (g/m³).

(c) Cumulus Clouds and Cumulonimbus Clouds

Cumulus Clouds Cumulonimbus Clouds
They are formed due to the vertical movement of air. They develop when cumulus clouds grow vertically.
They appear white or grey and dome-shaped. They appear as huge dark clouds with an anvil-shaped top.
They indicate fair weather. They bring thunder, lightning and heavy rainfall.

Q.4 Answer the following questions.

(a) Why is the air in a region dry?
Ans: The air in a region becomes dry because it contains very little moisture or water vapour.
(b) How is humidity measured?
Ans:
  • Absolute humidity is the amount of water vapour present in 1 cubic metre of air.
  • Formula:
Absolute Humidity = Mass of Water Vapour ÷ Volume of Air
  • Relative humidity is the percentage of water vapour present compared to the vapour-holding capacity of air.
Relative Humidity (%) = (Absolute Humidity ÷ Vapour-holding Capacity) × 100
(c) What are the prerequisites for condensation?
Ans: High relative humidity and the air reaching its dew point temperature are the two main prerequisites for condensation.
(d) What is a cloud? Write its types.
Ans: A cloud is a visible mass of tiny water droplets or ice crystals formed around dust particles at high altitudes.

The main types of clouds are:
  • High Clouds
  • Medium Clouds
  • Low Clouds
  • Cumulonimbus Clouds
(e) Which type of clouds give rain?
Ans: Nimbostratus and Cumulonimbus clouds bring rainfall.
(f) On what does the percentage of relative humidity depend?
Ans: The percentage of relative humidity depends on the absolute humidity and the vapour-holding capacity of air at a particular temperature.

Q.5 Give geographical reasons.

(a) Clouds float in the sky.
Ans:
  • Clouds are made up of tiny water droplets or ice crystals.
  • These particles are extremely light.
  • Therefore, they remain suspended and float in the atmosphere.
(b) The proportion of relative humidity changes according to altitude.
Ans:
  • Temperature decreases with increasing altitude.
  • Cool air can hold less water vapour.
  • Therefore, the relative humidity changes with altitude.
(c) Air becomes saturated.
Ans:
  • Air becomes saturated when it contains the maximum amount of water vapour it can hold at a particular temperature.
  • At this stage, it cannot hold any more moisture.
(d) Cumulus clouds change into cumulonimbus clouds.
Ans:
  • Cumulus clouds grow vertically due to the upward movement of warm air.
  • When they become very tall, they develop into cumulonimbus clouds.
  • These clouds cause thunderstorms and heavy rainfall.

Q.6 Solve the following.

(a) Calculate the relative humidity.
Solution:
Relative Humidity = (18 ÷ 30.37) × 100

= 59.26%
Ans: The relative humidity is 59.26%.
(b) Calculate the absolute humidity.
Solution:
Absolute Humidity = 4.08 g ÷ 1 m³

= 4.08 g/m³
Ans: The absolute humidity is 4.08 g/m³.

Q.7 Collect the weather-related information from newspapers for the month of July. Relate the difference in the maximum and minimum temperatures with humidity.

Ans:
Students should collect weather information from newspapers for the month of July and complete this activity on their own.
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