Water in the AtmosphereClass 11 Fundamentals of Physical Geography NCERT Solutions
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Solution 1 of 10
Q11. Multiple choice questions.
(i) Which one of the following is the most important constituent of the atmosphere for human beings?
(a)
Water vapour
(b)
Nitrogen
(c)
Dust particle
(d)
Oxygen
Solution
(d) Oxygen
Explanation: While water vapour is crucial for weather phenomena as discussed in the chapter, oxygen is the most important constituent of the atmosphere for the survival of human beings as it is essential for respiration.
Q21. Multiple choice questions.
(ii) Which one of the following process is responsible for transforming liquid into vapour?
(a)
Condensation
(b)
Transpiration
(c)
Evaporation
(d)
Precipitation
Solution
(c) Evaporation
Explanation: The chapter states, "Evaporation is a process by which water is transformed from liquid to gaseous state."
Q31. Multiple choice questions.
(iii) The air that contains moisture to its full capacity :
(a)
Relative humidity
(b)
Specific humidity
(c)
Absolute humidity
(d)
Saturated air
Solution
(d) Saturated air
Explanation: According to the text, "The air containing moisture to its full capacity at a given temperature is said to be saturated."
Q41. Multiple choice questions.
(iv) Which one of the following is the highest cloud in the sky?
(a)
Cirrus
(b)
Stratus
(c)
Nimbus
(d)
Cumulus
Solution
(a) Cirrus
Explanation: The text specifies that "Cirrus clouds are formed at high altitudes (8,000 - 12,000 m)," which is the highest altitude range mentioned for any cloud type.
Q12. Answer the following questions in about 30 words.
(i) Name the three types of precipitation.
Solution
The three main types of precipitation are:
- Rainfall: Precipitation in the form of liquid water droplets.
- Snowfall: Precipitation in the form of fine flakes of snow, which are hexagonal ice crystals.
- Sleet and Hail: Sleet consists of frozen raindrops, while hail is composed of small, rounded solid pieces of ice.
Q22. Answer the following questions in about 30 words.
(ii) Explain relative humidity.
Solution
Relative humidity is the percentage of moisture present in the air compared to the maximum amount of moisture the air can hold at a specific temperature. It is affected by changes in air temperature; as temperature increases, the air's capacity to hold moisture also increases, which can lower the relative humidity if no moisture is added.
Q32. Answer the following questions in about 30 words.
(iii) Why does the amount of water vapour decreases rapidly with altitude?
Solution
The amount of water vapour decreases with altitude primarily because it is derived from evaporation and transpiration at the Earth's surface. Additionally, as altitude increases, the temperature of the air decreases. Colder air has a lower capacity to hold water vapour, causing the moisture content to reduce rapidly at higher elevations.
Q42. Answer the following questions in about 30 words.
(iv) How are clouds formed? Classify them.
Solution
Clouds are formed by the condensation of water vapour in the free air at considerable heights. This condensation occurs around tiny particles like dust and salt, known as hygroscopic nuclei, when moist air cools to its dew point.
Clouds are classified into four main types based on height and appearance:
- Cirrus: High-altitude, thin, and feathery clouds.
- Cumulus: Cotton-like clouds with a flat base, found at medium altitudes.
- Stratus: Layered clouds covering large parts of the sky.
- Nimbus: Dark, dense clouds at low or middle levels that are associated with precipitation.
Q13. Answer the following questions in about 150 words.
(i) Discuss the salient features of the world distribution of precipitation.
Solution
The distribution of precipitation across the world is uneven and influenced by several factors. The salient features are as follows:
- General Trend: In general, rainfall decreases as one moves from the equator towards the poles.
- Land and Water Bodies: Coastal areas receive more rainfall than the interior of continents. Similarly, oceans receive more rainfall than landmasses because they are the primary source of water vapour.
- Latitudinal Variation: Between 35° and 40° N and S latitudes, the eastern coasts receive heavier rain, which decreases westward. In contrast, between 45° and 65° N and S latitudes, the westerlies cause heavy rainfall on the western margins of continents, which decreases eastward.
- Topography: Mountains that run parallel to the coast cause heavy rainfall on the windward side, while the leeward side remains dry and is known as a rain-shadow area.
- Precipitation Regimes: The world has different precipitation regimes. Heavy rainfall (over 200 cm) occurs in the equatorial belt and windward slopes of mountains in cool temperate zones. Moderate rainfall (100-200 cm) is found in interior continental areas. Low rainfall (50-100 cm) occurs in central tropical lands and temperate interiors, while very low rainfall (less than 50 cm) is characteristic of rain-shadow zones and high latitudes.
Q23. Answer the following questions in about 150 words.
(ii) What are forms of condensation? Describe the process of dew and frost formation.
Solution
Condensation is the transformation of water vapour into water. The forms of condensation depend on temperature and location. The main forms are dew, frost, fog, and clouds.
Dew Formation:
Dew consists of water droplets that form when moisture from the air is deposited on cooler solid surfaces like stones, grass, and leaves. It does not form around nuclei in the air but directly on objects. The ideal conditions for dew formation are a clear sky, calm air, high relative humidity, and long, cold nights. For dew to form, it is essential that the dew point (the temperature at which saturation occurs) is above the freezing point (0°C).
Frost Formation:
Frost forms under similar conditions to dew but occurs when the condensation takes place at or below the freezing point (0°C). In this case, the excess moisture in the air is deposited directly as minute ice crystals on cold surfaces, instead of water droplets. The ideal conditions for frost are the same as for dew (clear sky, calm air, high relative humidity), with the crucial difference that the air temperature must be at or below freezing.