Selina Textbook Solutions: Humidity | Geography Class 9 ICSE PDF Download

 Page 1


Humidity 
Exercises 
I. Short Answer Questions. 
Question 1. 
Define the following terms : 
(a) Precipitation 
(b) Evaporation 
(c) Condensation 
(d) Humidity 
(e) Latent heat. 
Answer: 
(a) Precipitation — It is process by which condensation in different forms falling on the 
ground e.g. rainfall, snowfall, drizzle, sleet and hail etc. 
(b) Evaporation — It is the process of converting water into water droplets and vapour. 
(c) Condensation — It is the process of converting the water- droplets into water. 
(d) Humidity — It is the amount of moisture present in the atmospheric air. 
(e) Latent heat — It is the unseen heat absorbed by the atmospheric air to form vapour 
after reaching boiling point of 100°C of water. 
Question 2. 
What determines the amount of water vapour in the air? 
Answer: 
The amount of water vapour or humidity is dependent on the temperature conditions, 
because the capacity of air to hold moisture changes according to the temperature, e.g., 
in higher temperature the water vapour amount may increase and in low temperature it 
may decrease. 
Question 3. 
How is relative humidity determined ? 
Answer: 
Relative humidity is the percentage of water vapour with respect to the amount of air at 
a particular temperature. 
 
Page 2


Humidity 
Exercises 
I. Short Answer Questions. 
Question 1. 
Define the following terms : 
(a) Precipitation 
(b) Evaporation 
(c) Condensation 
(d) Humidity 
(e) Latent heat. 
Answer: 
(a) Precipitation — It is process by which condensation in different forms falling on the 
ground e.g. rainfall, snowfall, drizzle, sleet and hail etc. 
(b) Evaporation — It is the process of converting water into water droplets and vapour. 
(c) Condensation — It is the process of converting the water- droplets into water. 
(d) Humidity — It is the amount of moisture present in the atmospheric air. 
(e) Latent heat — It is the unseen heat absorbed by the atmospheric air to form vapour 
after reaching boiling point of 100°C of water. 
Question 2. 
What determines the amount of water vapour in the air? 
Answer: 
The amount of water vapour or humidity is dependent on the temperature conditions, 
because the capacity of air to hold moisture changes according to the temperature, e.g., 
in higher temperature the water vapour amount may increase and in low temperature it 
may decrease. 
Question 3. 
How is relative humidity determined ? 
Answer: 
Relative humidity is the percentage of water vapour with respect to the amount of air at 
a particular temperature. 
 
Question 4. 
Name four chief forms of condensation. 
Answer: 
Four chief forms of condensation are clouds, fog, mist and dew droplets. 
Question 5. 
Mention the different forms of precipitation. 
Answer: 
Different forms of precipitation are rainfall, drizzling, hailstones, snowfall and sleet etc. 
Question 6. 
What do you understand by ‘condensation nuclei’ ? 
Answer: 
Condensation nuclei — Condensation nuclei is the base around which moisture is 
gathered and converts into a drop of water, e.g. the dust particles present in the 
atmosphere make the base of condensation form. 
Question 7. 
State the three types of rainfall. 
Answer: 
? Relief Rainfall – It occurs from the cooling of warm moist air which ascends 
above the mountain barrier lying in the direction of the prevailing winds. 
? Cyclonic or Frontal Rainfall – It occurs when warm and cold air masses confront 
each other, the warmer air generally climbs above the colder air. 
? Convectional Rainfall – Ascending currents of hot and humid air causes 
condensation of the clouds, resulting in heavy rainfall. 
Question 8. 
What is cyclonic rainfall ? 
Answer: 
Cyclonic rainfall is provided by the cyclones created in tropical and temperate regions 
along the air mass fronts, where warm and cold air meet together and the warm air is 
encircled by the cold air resulting in circular wind systems. The tropical cyclones provide 
heavy rainfall for a few days, but temperate cyclones provide light rainfall or drizzling for 
a long period. 
Question 9. 
How does latitude affect evaporation ? 
Answer: 
Evaporation is highest in the tropical belt due to continuous vertical rays of the sun, 
while in temperate belt less evaporation and in polar belt least evaporation takes place 
due to less insolation. 
Page 3


Humidity 
Exercises 
I. Short Answer Questions. 
Question 1. 
Define the following terms : 
(a) Precipitation 
(b) Evaporation 
(c) Condensation 
(d) Humidity 
(e) Latent heat. 
Answer: 
(a) Precipitation — It is process by which condensation in different forms falling on the 
ground e.g. rainfall, snowfall, drizzle, sleet and hail etc. 
(b) Evaporation — It is the process of converting water into water droplets and vapour. 
(c) Condensation — It is the process of converting the water- droplets into water. 
(d) Humidity — It is the amount of moisture present in the atmospheric air. 
(e) Latent heat — It is the unseen heat absorbed by the atmospheric air to form vapour 
after reaching boiling point of 100°C of water. 
Question 2. 
What determines the amount of water vapour in the air? 
Answer: 
The amount of water vapour or humidity is dependent on the temperature conditions, 
because the capacity of air to hold moisture changes according to the temperature, e.g., 
in higher temperature the water vapour amount may increase and in low temperature it 
may decrease. 
Question 3. 
How is relative humidity determined ? 
Answer: 
Relative humidity is the percentage of water vapour with respect to the amount of air at 
a particular temperature. 
 
Question 4. 
Name four chief forms of condensation. 
Answer: 
Four chief forms of condensation are clouds, fog, mist and dew droplets. 
Question 5. 
Mention the different forms of precipitation. 
Answer: 
Different forms of precipitation are rainfall, drizzling, hailstones, snowfall and sleet etc. 
Question 6. 
What do you understand by ‘condensation nuclei’ ? 
Answer: 
Condensation nuclei — Condensation nuclei is the base around which moisture is 
gathered and converts into a drop of water, e.g. the dust particles present in the 
atmosphere make the base of condensation form. 
Question 7. 
State the three types of rainfall. 
Answer: 
? Relief Rainfall – It occurs from the cooling of warm moist air which ascends 
above the mountain barrier lying in the direction of the prevailing winds. 
? Cyclonic or Frontal Rainfall – It occurs when warm and cold air masses confront 
each other, the warmer air generally climbs above the colder air. 
? Convectional Rainfall – Ascending currents of hot and humid air causes 
condensation of the clouds, resulting in heavy rainfall. 
Question 8. 
What is cyclonic rainfall ? 
Answer: 
Cyclonic rainfall is provided by the cyclones created in tropical and temperate regions 
along the air mass fronts, where warm and cold air meet together and the warm air is 
encircled by the cold air resulting in circular wind systems. The tropical cyclones provide 
heavy rainfall for a few days, but temperate cyclones provide light rainfall or drizzling for 
a long period. 
Question 9. 
How does latitude affect evaporation ? 
Answer: 
Evaporation is highest in the tropical belt due to continuous vertical rays of the sun, 
while in temperate belt less evaporation and in polar belt least evaporation takes place 
due to less insolation. 
Question 10. 
Why is evaporation maximum in tropical deserts surrounded by seas ? 
Answer: 
In tropical deserts, surrounded by seas, evaporation is maximum because of high 
temperatures and clear skies. 
Question 11. 
State the factors favouring evaporation. 
Answer: 
The conditions favourable for evaporation are high temperature and large amount of 
water of ocean, rainfall water etc. 
Question 12. 
What is the instrument used for measuring humidity? 
Answer: 
Hygrometer or Dry and Wet Bulb Thermometer is used to measure humidity. 
Question 13. 
State the process of clouds formation. Name the types of clouds. 
Answer: 
When the water vapour converts into the water droplets floating in the air, the clouds are 
formed. Main types of clouds are Cirrus, Cumulus, Altus and Stratus. 
Question 14. 
Name the regions which receive rainfall only in summer. 
Answer: 
The continental interiors in the sub-tropical regions get rainfall only in summer, e.g. 
Mangolia, Tibet etc. 
Question 15. 
Name two regions of heavy rainfall. 
Answer: 
Equatorial region and monsoon tropical region get highest rainfall. Highest rainfall is 
recorded in Cherrapunji and Mawsynram (1080 cm) in the world. 
Question 16. 
Describe the three chief ways in which condensation occurs. 
Answer: 
Three chief ways to assist condensation are : 
1. High amount of moisture present in atmosphere. 
2. The elements providing the nuclei for it should be present in atmosphere, e.g., 
dust particles, salt and smoke etc. 
Page 4


Humidity 
Exercises 
I. Short Answer Questions. 
Question 1. 
Define the following terms : 
(a) Precipitation 
(b) Evaporation 
(c) Condensation 
(d) Humidity 
(e) Latent heat. 
Answer: 
(a) Precipitation — It is process by which condensation in different forms falling on the 
ground e.g. rainfall, snowfall, drizzle, sleet and hail etc. 
(b) Evaporation — It is the process of converting water into water droplets and vapour. 
(c) Condensation — It is the process of converting the water- droplets into water. 
(d) Humidity — It is the amount of moisture present in the atmospheric air. 
(e) Latent heat — It is the unseen heat absorbed by the atmospheric air to form vapour 
after reaching boiling point of 100°C of water. 
Question 2. 
What determines the amount of water vapour in the air? 
Answer: 
The amount of water vapour or humidity is dependent on the temperature conditions, 
because the capacity of air to hold moisture changes according to the temperature, e.g., 
in higher temperature the water vapour amount may increase and in low temperature it 
may decrease. 
Question 3. 
How is relative humidity determined ? 
Answer: 
Relative humidity is the percentage of water vapour with respect to the amount of air at 
a particular temperature. 
 
Question 4. 
Name four chief forms of condensation. 
Answer: 
Four chief forms of condensation are clouds, fog, mist and dew droplets. 
Question 5. 
Mention the different forms of precipitation. 
Answer: 
Different forms of precipitation are rainfall, drizzling, hailstones, snowfall and sleet etc. 
Question 6. 
What do you understand by ‘condensation nuclei’ ? 
Answer: 
Condensation nuclei — Condensation nuclei is the base around which moisture is 
gathered and converts into a drop of water, e.g. the dust particles present in the 
atmosphere make the base of condensation form. 
Question 7. 
State the three types of rainfall. 
Answer: 
? Relief Rainfall – It occurs from the cooling of warm moist air which ascends 
above the mountain barrier lying in the direction of the prevailing winds. 
? Cyclonic or Frontal Rainfall – It occurs when warm and cold air masses confront 
each other, the warmer air generally climbs above the colder air. 
? Convectional Rainfall – Ascending currents of hot and humid air causes 
condensation of the clouds, resulting in heavy rainfall. 
Question 8. 
What is cyclonic rainfall ? 
Answer: 
Cyclonic rainfall is provided by the cyclones created in tropical and temperate regions 
along the air mass fronts, where warm and cold air meet together and the warm air is 
encircled by the cold air resulting in circular wind systems. The tropical cyclones provide 
heavy rainfall for a few days, but temperate cyclones provide light rainfall or drizzling for 
a long period. 
Question 9. 
How does latitude affect evaporation ? 
Answer: 
Evaporation is highest in the tropical belt due to continuous vertical rays of the sun, 
while in temperate belt less evaporation and in polar belt least evaporation takes place 
due to less insolation. 
Question 10. 
Why is evaporation maximum in tropical deserts surrounded by seas ? 
Answer: 
In tropical deserts, surrounded by seas, evaporation is maximum because of high 
temperatures and clear skies. 
Question 11. 
State the factors favouring evaporation. 
Answer: 
The conditions favourable for evaporation are high temperature and large amount of 
water of ocean, rainfall water etc. 
Question 12. 
What is the instrument used for measuring humidity? 
Answer: 
Hygrometer or Dry and Wet Bulb Thermometer is used to measure humidity. 
Question 13. 
State the process of clouds formation. Name the types of clouds. 
Answer: 
When the water vapour converts into the water droplets floating in the air, the clouds are 
formed. Main types of clouds are Cirrus, Cumulus, Altus and Stratus. 
Question 14. 
Name the regions which receive rainfall only in summer. 
Answer: 
The continental interiors in the sub-tropical regions get rainfall only in summer, e.g. 
Mangolia, Tibet etc. 
Question 15. 
Name two regions of heavy rainfall. 
Answer: 
Equatorial region and monsoon tropical region get highest rainfall. Highest rainfall is 
recorded in Cherrapunji and Mawsynram (1080 cm) in the world. 
Question 16. 
Describe the three chief ways in which condensation occurs. 
Answer: 
Three chief ways to assist condensation are : 
1. High amount of moisture present in atmosphere. 
2. The elements providing the nuclei for it should be present in atmosphere, e.g., 
dust particles, salt and smoke etc. 
3. The air should be saturated i.e. the relative humidity must be 100% to create dew 
point or the temperature should be below dew point. 
II. Give reasons for each of the following  
Question 1. 
In Equatorial regions the sky often remains overcast with clouds. 
Answer: 
Due to excessive heat the evaporation takes place in fast speed, and in every afternoon 
rainfall occurs after heavy cloud formation by convection process. So the sky mostly 
remains overcast with clouds. 
Question 2. 
Human comfort depends on humidity. 
Answer: 
Human efficiency is best at 40% relative humidity. More or less humidity creates 
uneasiness of humidity and dryness. 
Question 3. 
Condensation is the reverse process of evaporation. 
Answer: 
Condensation takes place upto the dew-point comes, but after it precipitation starts due 
to water-droplets converted into water drops. So, condensation and precipitation are 
different processes occurring in different conditions and temperature episodes. 
Question 4. 
Coasts receive more rainfall than the interior of the continents. 
Answer: 
Moisture-laiden winds provide more rainfall to the coastal parts due to being situated by 
the coast and receiving the rain bearing winds, but the interior get negligible rainfall due 
to being the almost dry winds without moisture. 
Question 5. 
The windward sides of mountains receive more rainfall than the leeward sides. 
Answer: 
The windward sides of mountainous slopes get ample rainfall by striking with the rain 
bearing winds first, while the leeward sides cannot get sufficient rainfall due to being on 
other side where the winds become almost dry due to imparting rainfall in windward due 
to loss of major part of moisture and water drops. 
Page 5


Humidity 
Exercises 
I. Short Answer Questions. 
Question 1. 
Define the following terms : 
(a) Precipitation 
(b) Evaporation 
(c) Condensation 
(d) Humidity 
(e) Latent heat. 
Answer: 
(a) Precipitation — It is process by which condensation in different forms falling on the 
ground e.g. rainfall, snowfall, drizzle, sleet and hail etc. 
(b) Evaporation — It is the process of converting water into water droplets and vapour. 
(c) Condensation — It is the process of converting the water- droplets into water. 
(d) Humidity — It is the amount of moisture present in the atmospheric air. 
(e) Latent heat — It is the unseen heat absorbed by the atmospheric air to form vapour 
after reaching boiling point of 100°C of water. 
Question 2. 
What determines the amount of water vapour in the air? 
Answer: 
The amount of water vapour or humidity is dependent on the temperature conditions, 
because the capacity of air to hold moisture changes according to the temperature, e.g., 
in higher temperature the water vapour amount may increase and in low temperature it 
may decrease. 
Question 3. 
How is relative humidity determined ? 
Answer: 
Relative humidity is the percentage of water vapour with respect to the amount of air at 
a particular temperature. 
 
Question 4. 
Name four chief forms of condensation. 
Answer: 
Four chief forms of condensation are clouds, fog, mist and dew droplets. 
Question 5. 
Mention the different forms of precipitation. 
Answer: 
Different forms of precipitation are rainfall, drizzling, hailstones, snowfall and sleet etc. 
Question 6. 
What do you understand by ‘condensation nuclei’ ? 
Answer: 
Condensation nuclei — Condensation nuclei is the base around which moisture is 
gathered and converts into a drop of water, e.g. the dust particles present in the 
atmosphere make the base of condensation form. 
Question 7. 
State the three types of rainfall. 
Answer: 
? Relief Rainfall – It occurs from the cooling of warm moist air which ascends 
above the mountain barrier lying in the direction of the prevailing winds. 
? Cyclonic or Frontal Rainfall – It occurs when warm and cold air masses confront 
each other, the warmer air generally climbs above the colder air. 
? Convectional Rainfall – Ascending currents of hot and humid air causes 
condensation of the clouds, resulting in heavy rainfall. 
Question 8. 
What is cyclonic rainfall ? 
Answer: 
Cyclonic rainfall is provided by the cyclones created in tropical and temperate regions 
along the air mass fronts, where warm and cold air meet together and the warm air is 
encircled by the cold air resulting in circular wind systems. The tropical cyclones provide 
heavy rainfall for a few days, but temperate cyclones provide light rainfall or drizzling for 
a long period. 
Question 9. 
How does latitude affect evaporation ? 
Answer: 
Evaporation is highest in the tropical belt due to continuous vertical rays of the sun, 
while in temperate belt less evaporation and in polar belt least evaporation takes place 
due to less insolation. 
Question 10. 
Why is evaporation maximum in tropical deserts surrounded by seas ? 
Answer: 
In tropical deserts, surrounded by seas, evaporation is maximum because of high 
temperatures and clear skies. 
Question 11. 
State the factors favouring evaporation. 
Answer: 
The conditions favourable for evaporation are high temperature and large amount of 
water of ocean, rainfall water etc. 
Question 12. 
What is the instrument used for measuring humidity? 
Answer: 
Hygrometer or Dry and Wet Bulb Thermometer is used to measure humidity. 
Question 13. 
State the process of clouds formation. Name the types of clouds. 
Answer: 
When the water vapour converts into the water droplets floating in the air, the clouds are 
formed. Main types of clouds are Cirrus, Cumulus, Altus and Stratus. 
Question 14. 
Name the regions which receive rainfall only in summer. 
Answer: 
The continental interiors in the sub-tropical regions get rainfall only in summer, e.g. 
Mangolia, Tibet etc. 
Question 15. 
Name two regions of heavy rainfall. 
Answer: 
Equatorial region and monsoon tropical region get highest rainfall. Highest rainfall is 
recorded in Cherrapunji and Mawsynram (1080 cm) in the world. 
Question 16. 
Describe the three chief ways in which condensation occurs. 
Answer: 
Three chief ways to assist condensation are : 
1. High amount of moisture present in atmosphere. 
2. The elements providing the nuclei for it should be present in atmosphere, e.g., 
dust particles, salt and smoke etc. 
3. The air should be saturated i.e. the relative humidity must be 100% to create dew 
point or the temperature should be below dew point. 
II. Give reasons for each of the following  
Question 1. 
In Equatorial regions the sky often remains overcast with clouds. 
Answer: 
Due to excessive heat the evaporation takes place in fast speed, and in every afternoon 
rainfall occurs after heavy cloud formation by convection process. So the sky mostly 
remains overcast with clouds. 
Question 2. 
Human comfort depends on humidity. 
Answer: 
Human efficiency is best at 40% relative humidity. More or less humidity creates 
uneasiness of humidity and dryness. 
Question 3. 
Condensation is the reverse process of evaporation. 
Answer: 
Condensation takes place upto the dew-point comes, but after it precipitation starts due 
to water-droplets converted into water drops. So, condensation and precipitation are 
different processes occurring in different conditions and temperature episodes. 
Question 4. 
Coasts receive more rainfall than the interior of the continents. 
Answer: 
Moisture-laiden winds provide more rainfall to the coastal parts due to being situated by 
the coast and receiving the rain bearing winds, but the interior get negligible rainfall due 
to being the almost dry winds without moisture. 
Question 5. 
The windward sides of mountains receive more rainfall than the leeward sides. 
Answer: 
The windward sides of mountainous slopes get ample rainfall by striking with the rain 
bearing winds first, while the leeward sides cannot get sufficient rainfall due to being on 
other side where the winds become almost dry due to imparting rainfall in windward due 
to loss of major part of moisture and water drops. 
III. Match the following 
 
Answer: 
 
 
IV. Long Answer Questions. 
Question 1. 
Distinguish between Absolute Humidity and Relative Humidity. 
Answer: 
Absolute Humidity : 
1. It is the measure of the actual amount of water vapour in the air, regardless of 
temperature. 
2. It is expressed as grams of moisture per cubic meter of air(g/m3). 
3. The higher the amount of water vapour, the higher is the absolute humidity. 
4. In weather calculations, absolute humidity is generally not taken into account. 
Relative Humidity: 
1. It measures water vapour in air but relative to the maximum vapour that the air 
can hold at that temperature.