Composition and Structure of AtmosphereClass 11 Fundamentals of Physical Geography NCERT Solutions
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Q11. Multiple choice questions.
(i) Which one of the following gases constitutes the major portion of the atmosphere?
(a)
Oxygen
(b)
Nitrogen
(c)
Argon
(d)
Carbon dioxide
Solution
(b) Nitrogen
Nitrogen is the most abundant gas, making up the major portion of the atmosphere's composition.
Q11. Multiple choice questions.
(i) Which one of the following gases constitutes the major portion of the atmosphere?
(a)
Oxygen
(b)
Nitrogen
(c)
Argon
(d)
Carbon dioxide
Solution
(b) Nitrogen is the correct answer. While the provided text focuses on the meteorological importance of gases like oxygen and carbon dioxide, nitrogen is the most abundant gas, constituting the major portion of the atmosphere.
Q21. Multiple choice questions.
(ii) Atmospheric layer important for human beings is:
(a)
Stratosphere
(b)
Mesosphere
(c)
Troposphere
(d)
Ionosphere
Solution
(c) Troposphere is the correct answer. The text states that the troposphere is the most important layer for all biological activity, as it contains the air we breathe, water vapour, and is where all weather phenomena occur.
Q21. Multiple choice questions.
(ii) Atmospheric layer important for human beings is:
(a)
Stratosphere
(b)
Mesosphere
(c)
Troposphere
(d)
Ionosphere
Solution
(c) Troposphere
The troposphere is the most important layer for all biological activity. It contains the air we breathe, and all weather and climate changes that affect life on Earth occur in this layer.
Q31. Multiple choice questions.
(iii) Sea salt, pollen, ash, smoke soot, fine soil - these are associated with:
(a)
Gases
(b)
Dust particles
(c)
Water vapour
(d)
Meteors
Solution
(b) Dust particles
These are all examples of small solid particles found in the atmosphere, which originate from various sources like sea salts, fine soil, smoke-soot, ash, and pollen.
Q31. Multiple choice questions.
(iii) Sea salt, pollen, ash, smoke soot, fine soil - these are associated with:
(a)
Gases
(b)
Dust particles
(c)
Water vapour
(d)
Meteors
Solution
(b) Dust particles is the correct answer. The chapter explicitly lists these items as examples of small solid particles that the atmosphere holds, originating from various sources like sea salts, fine soil, smoke-soot, ash, and pollen.
Q41. Multiple choice questions.
(iv) Oxygen gas is in negligible quantity at the height of atmosphere:
(a)
90 km
(b)
120 km
(c)
100 km
(d)
150 km
Solution
(b) 120 km is the correct answer. The text clearly mentions under the 'Composition of the Atmosphere' section that "oxygen will be almost in negligible quantity at the height of 120 km."
Q41. Multiple choice questions.
(iv) Oxygen gas is in negligible quantity at the height of atmosphere:
(a)
90 km
(b)
120 km
(c)
100 km
(d)
150 km
Solution
(b) 120 km
According to the chapter, the proportion of gases changes in the higher layers of the atmosphere, and oxygen becomes almost negligible at a height of 120 km.
Q51. Multiple choice questions.
(v) Which one of the following gases is transparent to incoming solar radiation and opaque to outgoing terrestrial radiation?
(a)
Oxygen
(b)
Nitrogen
(c)
Helium
(d)
Carbon dioxide
Solution
(d) Carbon dioxide
Carbon dioxide is a meteorologically important gas because it allows incoming solar radiation to pass through but absorbs the outgoing terrestrial radiation, contributing to the greenhouse effect.
Q51. Multiple choice questions.
(v) Which one of the following gases is transparent to incoming solar radiation and opaque to outgoing terrestrial radiation?
(a)
Oxygen
(b)
Nitrogen
(c)
Helium
(d)
Carbon dioxide
Solution
(d) Carbon dioxide is the correct answer. The chapter states that carbon dioxide is meteorologically very important because it is "transparent to the incoming solar radiation but opaque to the outgoing terrestrial radiation," which is the primary mechanism of the greenhouse effect.
Q12. Answer the following questions in about 30 words.
(i) What do you understand by atmosphere?
Solution
The atmosphere is a mixture of different gases that envelops the Earth. It is an integral part of the Earth's mass and contains life-sustaining gases like oxygen for animals and carbon dioxide for plants. Ninety-nine percent of its total mass is confined to a height of 32 km from the Earth's surface.
Q12. Answer the following questions in about 30 words.
(i) What do you understand by atmosphere?
Solution
The atmosphere is a mixture of different gases that envelopes the Earth. It is an integral part of the Earth's mass and contains life-giving gases like oxygen for animals and carbon dioxide for plants. 99 per cent of its total mass is confined to a height of 32 km from the Earth's surface.
Q22. Answer the following questions in about 30 words.
(ii) What are the elements of weather and climate?
Solution
The main elements of weather and climate are the atmospheric conditions that are subject to change and influence human life. These elements include temperature, pressure, winds, humidity, clouds, and precipitation.
Q22. Answer the following questions in about 30 words.
(ii) What are the elements of weather and climate?
Solution
The main elements of weather and climate are the atmospheric conditions that are subject to change and influence human life. These elements, as listed in the chapter, are temperature, pressure, winds, humidity, clouds, and precipitation.
Q32. Answer the following questions in about 30 words.
(iii) Describe the composition of atmosphere.
Solution
The atmosphere is composed of three main components: gases, water vapour, and dust particles. Gases like carbon dioxide and ozone play crucial roles. Water vapour is a variable gas that absorbs heat, and dust particles act as nuclei for condensation to form clouds.
Q32. Answer the following questions in about 30 words.
(iii) Describe the composition of atmosphere.
Solution
The atmosphere is primarily composed of three main components: gases, water vapour, and dust particles. Gases like oxygen and carbon dioxide are vital for life. Water vapour is a variable gas that absorbs heat and contributes to atmospheric stability. Dust particles act as nuclei for condensation to form clouds.
Q42. Answer the following questions in about 30 words.
(iv) Why is troposphere the most important of all the layers of the atmosphere?
Solution
The troposphere is the most important layer for all biological activity because it contains the air we breathe, along with dust particles and water vapour. Furthermore, all changes in climate and weather, which directly impact life on Earth, take place within this lowermost layer of the atmosphere.
Q42. Answer the following questions in about 30 words.
(iv) Why is troposphere the most important of all the layers of the atmosphere?
Solution
The troposphere is the most important atmospheric layer because it contains the air essential for life and all biological activities occur here. Furthermore, all changes in climate and weather, such as the formation of clouds and rain, take place within this layer.
Q13. Answer the following questions in about 150 words.
(i) Describe the composition of the atmosphere.
Solution
The atmosphere is composed of a mixture of gases, water vapour, and dust particles. The proportions of these components vary with altitude and location.
-
Gases: The atmosphere contains several gases. Carbon dioxide is meteorologically significant as it is transparent to incoming solar radiation but opaque to outgoing terrestrial radiation, causing the greenhouse effect. Ozone, found between 10 and 50 km, is another crucial gas that absorbs harmful ultraviolet rays from the sun. The proportion of gases like oxygen becomes negligible at a height of 120 km.
-
Water Vapour: This is a variable gas that decreases with altitude and from the equator towards the poles. It can constitute up to four percent of the air by volume in warm, wet tropics. Water vapour absorbs parts of solar insolation and terrestrial radiation, acting like a blanket that moderates the Earth's temperature. It also influences atmospheric stability.
-
Dust Particles: The atmosphere holds various solid particles like sea salts, fine soil, ash, pollen, and soot. These are concentrated in the lower layers but can be transported to great heights by air currents. They play a critical role as hygroscopic nuclei, around which water vapour condenses to form clouds.
Q13. Answer the following questions in about 150 words.
(i) Describe the composition of the atmosphere.
Solution
The atmosphere is a mixture of various gases, water vapour, and dust particles. The composition of the atmosphere is as follows:
-
Gases: The atmosphere is composed of several gases. Carbon dioxide is a meteorologically significant gas as it is transparent to incoming solar radiation but opaque to outgoing terrestrial radiation, causing the greenhouse effect. Its volume has been rising due to the burning of fossil fuels. Ozone, found between 10 and 50 km, is another crucial gas that absorbs harmful ultraviolet rays from the sun. Oxygen becomes negligible at a height of 120 km.
-
Water Vapour: This is a variable gas that decreases with altitude and from the equator towards the poles. It can account for up to four per cent of the air by volume in warm, wet tropics. Water vapour absorbs parts of solar insolation and preserves the Earth's radiated heat, acting like a blanket. It also contributes to the stability and instability of the air.
-
Dust Particles: The atmosphere holds small solid particles from sources like sea salts, fine soil, smoke, ash, and pollen. These are concentrated in the lower layers and are more abundant in subtropical and temperate regions. These particles act as hygroscopic nuclei, around which water vapour condenses to form clouds.
Q23. Answer the following questions in about 150 words.
(ii) Draw a suitable diagram for the structure of the atmosphere and label it and describe it.
Solution
While a diagram cannot be drawn here, the structure of the atmosphere can be described as a series of five distinct layers based on temperature conditions. The density of the atmosphere is highest near the surface and decreases with altitude.
Description of the Layers of the Atmosphere:
-
Troposphere: This is the lowermost layer, with an average height of 13 km. Its thickness is greatest at the equator (about 18 km) and least near the poles (about 8 km). It contains dust particles and water vapour, and all weather phenomena occur here. Temperature decreases with height at a rate of 1°C for every 165 m. It is the most important layer for biological activity.
-
Stratosphere: Found above the tropopause, this layer extends up to a height of 50 km. A key feature of the stratosphere is the presence of the ozone layer, which absorbs harmful ultraviolet (UV) radiation from the sun, shielding life on Earth.
-
Mesosphere: This layer lies above the stratosphere and extends to a height of 80 km. In the mesosphere, the temperature again decreases with increasing altitude, reaching as low as minus 100°C at 80 km.
-
Thermosphere: Located above the mesosphere, this layer contains the ionosphere (between 80 and 400 km). The ionosphere has electrically charged particles called ions, which reflect radio waves back to Earth. In this layer, the temperature starts increasing with height.
-
Exosphere: This is the uppermost and highest layer of the atmosphere. Very little is known about it. The contents are extremely rarefied, and it gradually merges with outer space.
Q23. Answer the following questions in about 150 words.
(ii) Draw a suitable diagram for the structure of the atmosphere and label it and describe it.
Solution
The structure of the atmosphere is divided into five distinct layers based on temperature variations with altitude. A diagram would show these layers stacked vertically from the Earth's surface upwards.
Description of the Atmospheric Layers:
-
Troposphere: This is the lowermost layer, with an average height of 13 km. Its thickness is greatest at the equator (about 18 km) and least at the poles (about 8 km). It contains dust particles and water vapour, and all weather phenomena occur here. Temperature decreases with increasing altitude in this layer. It is the most important layer for all biological activities.
-
Stratosphere: Found above the troposphere and extending up to 50 km, this layer is separated from the troposphere by the tropopause. A key feature of the stratosphere is the presence of the ozone layer, which absorbs harmful ultraviolet radiation from the sun, protecting life on Earth.
-
Mesosphere: Lying above the stratosphere, this layer extends up to a height of 80 km. In the mesosphere, the temperature again starts to decrease with altitude, reaching as low as minus 100°C at its upper limit, the mesopause.
-
Thermosphere (Ionosphere): Located between 80 and 400 km above the mesopause, this layer contains electrically charged particles called ions. These ions reflect radio waves transmitted from the Earth back to the surface, enabling wireless communication. In this layer, the temperature starts increasing with height.
-
Exosphere: This is the uppermost and highest layer of the atmosphere. Very little is known about it, but its contents are extremely rarefied. It gradually merges with outer space.