RBSE Class 11 Geography Important Questions Chapter 11 Water in the Atmosphere

Rajasthan Board RBSE Class 11 Geography Important Questions Chapter 11 Water in the Atmosphere Important Questions and Answers. 

RBSE Class 11 Geography Important Questions Chapter 11 Water in the Atmosphere

Multiple Choice Questions

1. Beyond which distance, things are not visible due to Fog?
(A) 100 metres 
(B) 150 metres
(C) 200 metres 
(D) 250 metres.
Answer:
(C) 200 metres 

 

2. Upto which height, Low stratus clouds are found.
(A) 1000 metres 
(B) 2000 metres 
(C) 3000 metres 
(D) 4000 metres.
Answer:
(C) 3000 metres 

3. Which out of following are high clouds?
(A) Cirrus 
(B) Cumulus
(C) Stratus 
(D) Nimtous.
Answer:
(A) Cirrus 

4. Which type of rainfall occurs in Equaterial region?
(A) Convectional 
(B) Relief
(C) Cyclomic 
(D) Forntal.
Answer:
(A) Convectional 

5. What is average annual rainfall of world?
(A) 950 mm 
(B) 975 mm
(Q 9000 mm 
(D) 1000 mm.
Answer:
(B) 975 mm

6. How much water vapour is there in atmosphere?
(A) 1% 
(B) 2%
(C) 3% 
(D) 4%.
Answer:
(B) 2%

7. Ralative intensity is measured
(A) Hydrometer
(B) Hygrometer
(C) Barometer
(D) Ionometer.
Answer:
(A) Hydrometer

8. Which are the main reasons of low rainfall on the southern platau of India?
(A) High temperature
(B) Plateau Surface
(C) To be situated in rain shadow
(D) Low evaperation.
Answer:
(C) To be situated in rain shadow

9. Which is the area of highest rainfall in the world?
(A) Equatorial region
(B) Polar region
(C) Latitude 20°-30°
(D) Tropical region.
Answer:
(A) Equatorial region

10. What kind of rainfall occurs in Punjab winter?
(A) Orgographic rainfall
(B) Mounting rainfall
(C) Cyclonic rainfall
(D) Convectional rainfall.
Answer:
(C) Cyclonic rainfall

Short Answer Type Questions

Question 1. 
Name three sources of water vapour.
Answer: 
Oceans, lakes, rivers.

Question 2. 
Name the factors on which evaporation depends.
Answer: 
Aridity, temperature and movement of air.

Question 3. 
What is condensation?
Answer: 
Cooling of saturated air.

Question 4. 
At what temperature, does condensation take place?
Answer: 
At Dew Point.

Question 5. 
What is the percentage of humidity at dew point?
Answer:
100 per cent.

Question 6. 
State the different forms of condensation.
Answer: 
Frost and snow, dew, fog, mist, clouds.

Question 7. 
Name the instrument used for measuring humidity.
Answer: 
Hygrometer.

Question 8.
Name the two types of humidity.
Answer: 
Relative and Absolute humidity.

Question 9. 
In which unit, is relative humidity measured?
Answer: 
In percentages.

Question 10. 
What is the relation between relative humidity and rainfall?
Answer: 
When relative humidity is 100 per cent, rainfall takes place.

Question 11. 
Name the different forms of precipitation.
Answer: 
Rain, snow, hailstone.
 
Question 12. 
What is the general cause of rainfall?
Answer: 
Cooling of saturated air.

Question 13.
Which instrument is used to measure rainfall?
Answer: 
Rain gauge.

Question 14. 
Name the type of daily rainfall in the equatorial region.
Answer: 
Convectional rainfall.

Question 15. 
Name the dry area on the leeward slope of a mountain.
Answer: 
Rain-shadow.

Question 16. 
Name a rain-shadow area in India.
Answer: 
Deccan plateau.

Question 17. 
Which region gets mostly rainfall in winter?
Answer: 
Mediterranean Region.

Question 18. 
Which type of rainfall occurs in N.W. India during winter?
Answer: 
Cyclonic rainfall.

Short Answer Type Questions

Question 1. 
What do you mean by one centimetre of rainfall?
Answer: 
Rainfall is measured in centimetre. One centimetre of rainfall means the amount of water that would cover a uniformly flat ground to the depth of one centimetre provided that none of water is evaporated; drained away or sinks into the ground.

Question 2. 
What are clouds?
Answer:
Tiny droplets of water suspended in the air are known as clouds. These settle on the dust particles and float in the air as clouds. A cloud is a condensed moisture. It is formed by condensation of water vapour after dew point.

Question 3. 
What is meant by the term ‘Humidity’?
Answer: 
Humidity means the amount of water vapour present in an air. Water vapour is always present in an air. About 2% of the atmosphere consists of water vapour. Most of the water vapours of the atmosphere come from the oceans, lakes, rivers through evaporation.

Question 4. 
Define Evaporation. Name the factors controlling the amount and rate of evaporation.
Answer: 
Evaporation. The process by which water is changed into water vapour (liquid to gaseous) is known as evaporation. The amount and rate of evaporation depend upon the following factors :

1. Aridity. Dry air can absorb and retain more moisture than humid air.
2. Temperature. The higher the temperature, the higher is the rate of evaporation.
3. Movement of air. The greater the movement of the air, the greater is the evaporation.
4. Water bodies. Evaporation is greater on the oceans than on land.

Question 5. 
What is dew point? How is it related to the amount of moisture?
Answer:
Dew Point. The cooling of saturated air leads to condensation. The critical temperature at which the condensation of air begins is called Dew point. At dew point, an air is saturated to its maximum capacity. At dew point, the relative humidity is 100%.

Question 6. 
How does condensation take place? What are the different forms of condensation?
Answer: 
Condensation. Condensation is the process by which water vapour of the atmosphere is changed to water (from gaseous to liquid state). Condensation starts when the temperature falls below dew point.
Forms of condensation. Condensation takes place in different forms such as :

1. frost and snow.
2. dew, fog, mist, smog.
3. clouds, haze.

Question 7. 
Define precipitation. Name its different forms.
Answer: 
Precipitation. Precipitation means ‘throwing down of moisture’ from atmosphere. It is the collective name given to different forms of moisture falling on the earth. Precipitation can be liquid or solid. It occurs in the following forms:

1. Rainfall 
2. Snow 
3. Hail
4. Sleet 
5. Dew 
6. Frost 
7. Rime. 

Question 8. 
What is the relation between relative; ™ humidity and rainfall? 
Answer: 
As the relative humidity increases, the air becomes saturated. The relative humidity of the saturated air is 100 per cent. At this stage, air cannot hold any additional amount of moisture. Water vapour is condensed into water. The possibility of rain depends upon a high relative humidity.

Question 9. 
What do you mean by the term ‘Smog’?
Answer:
Smog is a combination of two words (smoke + fog). Very thick smoky fog is called smog. It is formed in industrial areas like Black country of Britain. It reduces the visibility to 200 metres.

Question 10. 
What is Haze? How is it caused?
Answer: 
Haze is caused by smoke and dust particles in individual areas. It is caused to unequal refraction of light in air of different densities. It is caused in areas of low humidity. It reduces the visibility to 2 kms.

Question 11. 
What is rain shadow? Name one part;
of the Indian sub-continent that experiences! rain shadow. 
Answer: 
The leeward slope where the air descends and is dry is called rain shadow. Descending winds become warm and dry. There is no condensation. Deccan plateau lies in the rain shadow of Western Ghats.

Question 12. 
Why does the equatorial region get daily rainfall in the afternoon?
Answer: 
Sun’s rays fall vertical on the equator throughout the year. The land is intensely heated. The air expands, becomes lighter, and rises as convection currents. The rising air leads to cooling and condensation. Thus, torrential rainfall occurs daily in the afternoon.

Question 13. 
How is rainfall caused?
Answer: 
Rainfall. Humidity is the basis of rain. The general cause of rainfall is the cooling of the saturated air. The mechanism of rainfall passes through many stages.
(i) Condensation. The moist rising air is cooled, saturated and condensation takes place.

(ii) Formation of clouds. Water vapour is condensed on the large number of dust particles to form clouds.

(iii) Formation of rain drops. The cloud droplets coalesce (merge) to form rain drops. One rain drop often contains one million cloud droplets. When these rain drops become so heavy that air cannot hold these, these fall on the earth in the form of rainfall. Thus, the release of moisture in the form of drops of water is called rainfall.

Question 14. 
How is rainfall shown on maps?
Answer: 
Rainfall is shown by isohytes on maps. Isohytes are lines joining the places of equal amount of rainfall
for a certain period. These lines are drawn by joining the places of equal rainfall.

Question 15. 
Discuss the processes of adiabatic heating and cooling.
Answer: 
Adiabatic heating. When air moves downward or descends along a leeward slope, it is compressed. Compression results in heating of the air. It is known as adiabatic heating. Adiabatic cooling. When the air moves upward it expands. Expansion results in cooling of the air. It occurs in ascending winds or convection currents. It is known as adiabatic cooling. It is the process by which the temperature of air is reduced below the dew point. This adiabatic cooling is responsible for formation of clouds and precipitation.

Question 16. 
Discuss the factors which control the distribution of rainfall.
Answer: 
The distribution of the rainfall in the world depends on the following factors :

1. Latitude. The amount of rainfall decreases from the equator towards the poles.
2. Distance from sea. Coastal areas get more rainfall than interiors of the continents.
3. Prevailing winds. Winds from sea bring rain, while winds from land are dry. Trade winds bring rain to the eastern parts, while the westerlies bring rain to the western parts.
4. Ocean currents. Winds blowing over warm ocean currents give rainfall over coastal areas. Cold currents increase the aridity of the coastal areas.
5. Altitude. Mountains force winds to rise and are areas of high rainfall.
6. The direction of Mountains. Mountains like Aravalis lying parallel to the direction of winds are unable to check the winds and do not help in getting rainfall.

Comparison Questions

Question 1. 
Distinguish between the following pairs :

1. Condensation and Evaporation.
2. Relative Humidity and Absolute Humidity.
3. Dew and Dew point.
4. Fog and Mist.
5. Precipitation and Rainfall.

(i) Condensation	Evaporation
1. Condensation is the process by which water vapour is changed to water.	1. Evaporation is the process by which water is changed to water vapour.
2. Cooling of air leads to condensation.	2. High temperatures favour evaporation.
3. This change takes place from gaseous to liquid condition.	3. This change takes place from liquid to gaseous con

 

C(ii) Relative Humidity	Absolute Humidity
1. It is a ratio between the actual amount of water vapour present in air at temperature and the maximum amount of water vapour that the air can hold at the temperature.	1. The total amount of water vapour present in air at a particular temperature is absolute humidity.
2. It is a ratio between the absolute humidity and vapour capacity of the air.	2. It is defined as weight of water vapour per unit volume of air.
3. It is maximum in equatorial regions, but is lowest in hot deserts.	3. It is maximum over oceans and lowest in high pressure areas.

 

(iii) Dew	Dew point
1. The droplets of water deposited on rocks, grass, leaves and the ground are termed as dew.	1. The temperature at which an air becomes saturated is called Dew point.
2. Air, near the ground is condensed to form drops.	2. Condensation of air be-gins at this tempera-ture.
3. Frozen drops of dew are known as frost.	3. The relative humidity at dew point is 100%.

 

Fog	Mist
1. Fog is condensed water vapours hanging in the air.	1. Thin fog is called mist.
2. The visibility is less than 200 metres.	2. Visibility is more that 200 metres.
3. Fog is formed due to cooling of	3. Mist is formed due to cooling of wet air by ra-diation.

 

Precipitation	Rainfall
1. It is the collective name given to different forms of release of moisture after condensation.	1. It is a type of precipita-on the earth in the form of droplets of water.
2. Precipitation has two forms : (a) liquid (b) solid.	2. When cloud particles grow heavy, they fall as rain drops (in liquid form).
3. Rainfall, snow, hail are the common forms of precipitation.	3. Three types of rainfall are convectional, relief and frontal.

 

Essay Type Questions

Question 1. 
Distinguish between Relative Humidity (g) and Absolute Humidity. Explain the relation between Relative Humidity and Rainfall.
Answer: 
Absolute Humidity. Total amount of water vapour present in air at a particular temperature is absolute humidity. It is defined as the weight of water vapour per unit volume of air. It is expressed as grams per cubic metre of air. Absolute humidity is not a reliable index. It changes with the changes in volume of air. So absolute humidity varies with contraction or expansion of the air.

Distribution :

1. Absolute humidity is maximum in the equatorial region.
2. It is more in summer than in winter. Similarly it is higher during the day than night.
3. Absolute humidity is higher over oceans than over land masses.
4. In areas of high pressure, absolute humidity is low due to descending winds.

Relative Humidity. Relative humidity is expressed as percentage. It is a ratio between the actual amount of the water vapour present in the air at a temperature and the maximum amount of water vapour which the same volume of air can hold at the given temperature.

\(\begin{gathered} \text { R.H. }=\frac{\text { Actual amount of water vapour present in air }}{\text { The max .amount of water vapour the same air }} \times 100 \\ \text { can hold at given temp. } \end{gathered}\)

In other words, it is a ratio, expressed in percentage, between the absolute humidity and the maximum vapour capacity of the air.

\(\text { R. H. }=\frac{\text { Absolute humidity }}{\text { Vapour capacity }} \times 100\)

Example. The air at 70° F temperature has 4 grains of water vapour per cubic ft. actually present. But the air at 70° F temp, can hold 8 grains of water vapour per cu. ft.

\(\therefore \quad \text { R.H. }=\frac{4}{8} \times 100=50 \%\)

When the relative humidity is 100 per cent, the air is fully saturated. Air with 50 per cent relative humidity would be half saturated. So relative humidity is the amount of saturation value expressed in percentages. The relative humidity changes with temperature and amount of water vapour. As the temperature increases, the air expands and its vapour capacity increases resulting in a low relative humidity. The relative humidity increases with a decrease in temperature or addition of water vapour.

Distribution :

1. The relative humidity is maximum at the equator and decreases polewards.
2. It is maximum in early morning and minimum in the afternoon.
3. It is low in hot deserts, in continental interiors, and in areas of anti-cyclonic conditions.
4. It is high during rainy season.

Relation between Relative Humidity and Rainfall. Relative humidity determines the rate and amount of evaporation. So it is an important climatic factor. As the relative humidity increases, the air becomes saturated. The relative humidity of the saturated air is 100 per cent. At this stage, air cannot hold any additional amount of moisture. Water vapour is condensed into water. The possibility of rain depends upon a high relative humidity.

Question 2. 
How is rainfall caused? Describe with examples, the different types of rainfall.
Answer: 
Rainfall. Humidity is the basis of rain. The general cause of rainfall is the cooling of saturated air. The mechanism of rainfall passes through many stages.
(i) Condensation. Due to adiabatic cooling (10° C per 1 km), the rising air is cooled. The moist air is saturated and condensation takes place.

(ii) Formation of clouds. Water vapour is condensed on a large number of dust particles floating in the air. These are known as hygroscopic particles. Cloud particles are formed on these. 

(iii) Formation of rain drops. The cloud particles are very small in size. These cloud droplets coalesce (merge) to form rain drops. One rain drop often contains one million cloud droplets. When these rain drops become so heavy that the air cannot hold these, they fall on the earth in the form of rainfall. Thus, the release of moisture in the form of drops of water is called rainfall.

Types of rainfall. On the basis of process of cooling of air, there are three types of rain :

1. When the air is cooled by rising convection currents.
2. When moist air is cooled due to ascent along a mountain barrier.
3. When air is cooled due to meeting of warm and cold air masses.

1. Convectional Rainfall. This type of rainfall is caused by convection currents. When the land is intensely heated, the hot air rises vertically as convection currents. As it rises, it expands and is cooled due to the release of pressure. The rising air is saturated and condensation takes place resulting in cumulus clouds. This self-generating mechanism results in torrential rainfall. The equatorial regions experience convectional rainfall. In this region, convectional system is best developed in the afternoon and gets heavy showers in the evening.

2. Orographic Rainfall. This type of rainfall is caused when moist air is forced to ascend a mountain barrier. The air rising up the mountain slope (windward slope) causes expansion, cooling and condensation. The windward slope gets the maximum rainfall. On the leeward slope, the air is descending. It increases the pressure and temperature as the air is compressed and warmed. There is evaporation but no condensation. These areas remain dry and are known as Rain-shadow areas. Since this type of rainfall is caused by relief of the land, it is known as relief rainfall. In summer, S. W. monsoons give heavy rainfall on the Western Ghats, but Deccan plateau is practically dry as it lies in the rain shadow of Western Ghats.

3. Frontal Rainfall. This type of rainfall is caused by convergence of warm and cold air masses along a front. The warm air is lighter and tends to rise over the cold air. In ascent, the pressure decreases, the air expands and cools and condensation takes place. As this rainfall is associated with cyclones, it is called as cyclonic rainfall. The rainfall is slow, continuous and extensive. The rain is common in N. W. Europe in winter. Punjab plains experience rainfall in winter from cyclones coming from Mediterranean Sea.

Question 3. 
How are Clouds formed? Discuss their types.
Answer:
Clouds.
Clouds are formed by the condensation of water vapour around nuclei of minute dust particles in the air. In most cases, clouds consist of tiny droplets of water, but they may also consist of ice particles if the temperature is below freezing point. Most clouds are formed by the rising warm and moist air. The ascending air expands and cools until the dew point is reached and some of the moisture condenses into clouds. Other clouds result from mixing between two air masses of different temperatures. (Fig. On next page) Clouds at and near the earth's surface are known as fog. The ten types of clouds are combined into three groups based mainly on the average height of the cloud base. They are as given below :

1. High clouds 5 to 14 km
2. Middle clouds 2 to 7 km
3. Low clouds below 2 km.
4. (iv) High Clouds.

(i) Cirrus (Ci). These are fibrous clouds with a delicate, silky appearance. When detached and arranged irregularly in the sky, they are harbingers of fair weather. On the other hand, when they are systematically arranged, as in bands, or connected with cirrostratus or altostratus, they usually foretell wet weather.

(ii) Cirrostratus (Cs). A thin, whitish sheet of cloud covering the whole sky and giving it a milky appearance is called cirrostratus. These clouds commonly produce a halo around the sun and the moon. They are usually signs of the approaching storm.

(iii) Cirrocumulus (Cc). These clouds appear as small white flakes or small globular masses, usually without shadows.
They are usually arranged in groups, lines or ripples resulting from undulation of the cloud sheet. Such an arrangement is called mackerel sky.

(II) Middle Clouds.
(i) Altostratus (As). A uniform sheet of cloud, gray or bluish in colour, and usually having a fibrous structure belong to this group. It often merges gradually with cirrostratus. The sun and the moon shine wanely through these clouds. Sometimes it also presents a corona. Altostratus commonly is followed by widespread and relatively continuous precipitation.

(ii) Altocumulus (Ac). These are flattened globular masses of clouds, arranged in lines or waves. They differ from cirrocumulus as they have larger globules, often with shadows.
 
(ID) Low Clouds.
(i) Stratocumulus (Sc). Large globular masses or rolls of soft gray clouds with brighter interstices belong to this group. The masses are commonly arranged in a regular pattern.

(ii) Stratus (St). These are low uniform layers of clouds resembling fog, but not resting on the ground. Thin stratus clouds produce a corona.

(iii) Nimbostratus (Ns). They are dense, shapeless and often ragged layers of low clouds, which commonly cause continuous rainfall.

(iv) Cumulus (Cu): These are thick, dense clouds with vertical development. The upper surface is dome shaped with a cauliflower structure, while the base is nearly horizontal. Most cumulus clouds are of fair weather type, although lowering cumulus may develop into cumulonimbus or thunderheads.

(v) Cumulonimbus (Cs). Heavy masses of cloud with great vertical development whose summit rise like mountains or towers is called cumulonimbus. An anvil-shaped top is its characteristic. It is often accompanied by heavy showers, squalls, thunderstorms, and sometimes hail

Source Based Questions 

1. Read the following paragraph and answer the questions given below:
Convectional rainfall is caused by convection currents. When the land is intensely heated, the hot air rises vertically as convection currents. As it rises, it expands and is cooled due to the release of pressure. The rising air is saturated and condensation takes place resulting in cumulus clouds. This self-generating mechanism results in torrential rainfall. The equatorial regions experience convectional rainfall. In this region, convectional system is the best developed in the afternoon and gets heavy showers in the evening.

(i) Which type of rainfall occurs in equatorial region?
(a) Convectional 
(b) Relief
(c) Cyclonic 
(d) Frontal
Answer: 
(a) Convectional

(ii) Which one of the following is the highest cloud in the sky?
(a) Cirrus 
(b) Nimbus
(c) Stratus 
(d) Cumulus
Answer: 
(a) Cirrus

(iii) Which type of rainfall is caused due to convection currents?
(a) Orographic 
(b) Relief
(c) Convection 
(d) Frontal
Answer: 
(c) Convection

(iv) Which area recieves convectional rainfall?
(a) Temperate region
(b) Equatorial region
(c) Tropical region
(d) Torrid region 
Answer: 
(b) Equatorial region

2. Read the following paragraph and answer the questions given below:
The distribution of rainfall is shown according to latitudes. This is known as zonal distribution. The average annual precipitation for the whole earth is about 975 mm. On the land, it is about 660 mm but in the ocean it is about 1100 mm. The maximum annual rainfall is about 1900 mm and it occurs in the equatorial zone between 10°N to 10° S latitudes. Between 20°-30° latitudes, the average annual rainfall is 800 mm. Between 45°-55° latitudes the average annual rainfall is the minimum about 1000 mm. Trade winds give rainfall in the eastern parts of the tropics. The continental interiors get low rainfall as compared to coastal areas.

(i) The distribution of rainfall according to latitudes is called
(a) Zonal
(b) State
(c) Centre 
(d) None of these
Answer: 
(a) Zonal

(ii) What is the average annual rainfall for the whole earth?
(a) 970 mm 
(b) 975 mm
(c) 980 mm 
(d) 985 mm
Answer: 
(b) 975 mm

(iii) What is the maximum annual rainfall?
(a) 1800 mm 
(b) 1700 mm
(c) 1500 mm 
(d) 1900 mm
Answer: 
(d) 1900 mm

(iv) Where annual average rainfall is 800 mm?
(a) 20°-30° latitudes
(b) 30°-40° latitudes
(c) 23.5°-0° latitudes
(d) All of these 
Answer: 
(a) 20°-30° latitudes 

HOTS QUESTIONS

Question 1
Write a note on Potential Evapo-: transpiration.
Answer: 
Potential Evapotranspiration:
Evapotranspiration is the amount of moisture transferred to the atmosphere by evaporation of liquid and solid water plus transpiration from living tissues principally from plants. The term ‘potential evapo- transpiration refers to idealised conditions in which there would be enough rainfall to provide sufficient moisture for all possible evapotranspiration in an area. In order to determine the potential evapotranspiration for any place or area, several factors like temperature, latitude, vegetation, permeability and water retention capacity of the soil are taken into consideration. Places having surplus precipitation over evapotranspiration are marked by a surplus of underground water storage. 

SELF EVALUATION TEST 

1. State the amount of water vapour present in atmosphere. 
2. Name two types of humidity. 
3. Name the type of rainfall which occurs daily in equatorial region. 
4. Name a rain shadow area in India. 
5. What is condensation? 
6. What is the general cause of rainfall? 
7. What is fog? 
8. Name three types of precipitation. 
9. Name three types of rainfal. 
10. Describe the different types of clouds.