Worksheet Solutions: Composition and Structure of Atmosphere | Geography Class 11 - Humanities/Arts PDF Download

Fill in the Blanks

Q1: Carbon dioxide is meteorologically important as it is transparent to incoming solar radiation but opaque to the outgoing terrestrial radiation. It largely contributes to the _______________ effect.
Ans: greenhouse effect.
The greenhouse effect is a natural phenomenon where certain gases in the Earth's atmosphere, such as carbon dioxide, trap heat from the sun, warming the planet. This is important for maintaining the Earth's temperature suitable for life.

Q2: The uppermost layer of the atmosphere is called the _______________.
Ans: exosphere.
The exosphere is the outermost layer of Earth's atmosphere, and it gradually transitions into outer space. It consists of very sparse gas molecules and is where satellites and other human-made objects in space orbit the Earth.

Q3: Water vapor decreases with altitude, and in the dry and cold areas of deserts and polar regions, it may be less than _______________ percent of the air.
Ans: 1.
This indicates that the air in extremely dry and cold regions, such as deserts and polar areas, contains very little moisture in the form of water vapor, often less than 1% of the air's composition.

Q4: Dust particles in the atmosphere include sea salts, fine soil, smoke-soot, ash, pollen, dust, and disintegrated particles of _______________.
Ans: volcanic eruptions.
Dust particles in the atmosphere can come from various sources, including volcanic eruptions. Volcanic eruptions release ash and fine particles into the atmosphere, which can have significant effects on climate and air quality.

Q5: The troposphere, the lowest layer of the atmosphere, is most important for all _______________ activity.
Ans: weather.
The troposphere is where weather phenomena occur, including the formation of clouds, precipitation, and various weather events. It is the layer closest to the Earth's surface and is where most of our weather takes place.

Q6: The layer that absorbs ultraviolet radiation and shields life on Earth from harmful energy is known as the _______________ layer.
Ans: ozone.
The ozone layer is a region in the stratosphere that contains a relatively high concentration of ozone (O₃) molecules. It plays a crucial role in absorbing and blocking a significant portion of the sun's harmful ultraviolet (UV) radiation, protecting life on Earth.

Q7: The zone separating the troposphere from the stratosphere is called the _______________.
Ans: tropopause.
The tropopause is a boundary or transition zone between the troposphere and the stratosphere. It represents a significant change in temperature and marks the point where weather processes in the troposphere give way to the stable conditions of the stratosphere.

Q8: The mesosphere extends up to a height of _______________ kilometers.
Ans: 85.
The mesosphere is a layer of the Earth's atmosphere located above the stratosphere and below the thermosphere. It extends up to an altitude of approximately 85 kilometers (about 53 miles) above the Earth's surface.

Q9: The ionosphere is located between _______________ and 400 kilometers above the mesopause.
Ans: 60.
The ionosphere is a region of the Earth's upper atmosphere that contains a high concentration of ions and free electrons. It typically extends from about 60 kilometers to 400 kilometers above the mesopause, and it plays a crucial role in reflecting and refracting radio waves.

Q10: The increase in the volume of carbon dioxide in the past few decades is mainly due to the burning of _______________.
Ans: fossil fuels.
The increase in atmospheric carbon dioxide (CO₂) levels is primarily attributed to the burning of fossil fuels, such as coal, oil, and natural gas. These activities release CO₂ into the atmosphere and contribute to the enhanced greenhouse effect and global warming.

Assertion and Reason Based

Q1: Assertion: Carbon dioxide is transparent to incoming solar radiation.
Reason: Carbon dioxide is responsible for the greenhouse effect.
(a) Both assertion and reason are true, and the reason is the correct explanation of the assertion.
(b) Both assertion and reason are true, but the reason is not the correct explanation of the assertion.
(c) Assertion is true, but the reason is false.
(d) Assertion is false, but the reason is true.
Ans: (a)
Carbon dioxide (CO₂) does allow incoming solar radiation (shortwave radiation) to pass through, but it becomes opaque to outgoing terrestrial radiation (longwave radiation). This property is essential for the greenhouse effect. The greenhouse effect occurs because gases like CO₂ trap heat within the Earth's atmosphere by preventing some of the heat from escaping into space. This trapped heat warms the planet. Therefore, both the assertion and the reason are true, and the reason explains why the assertion is correct.

Q2: Assertion: The stratosphere contains the ozone layer.
Reason: The ozone layer absorbs ultraviolet radiation.
(a) Both assertion and reason are true, and the reason is the correct explanation of the assertion.
(b) Both assertion and reason are true, but the reason is not the correct explanation of the assertion.
(c) Assertion is true, but the reason is false.
(d) Assertion is false, but the reason is true.
Ans: (a)
The assertion is true because the stratosphere is the layer of the atmosphere where the ozone layer is primarily located. The reason is also true because the ozone layer in the stratosphere indeed absorbs ultraviolet (UV) radiation from the sun, protecting life on Earth from harmful UV rays. The reason explains why the assertion is correct.

Q3: Assertion: The troposphere contains dust particles and water vapor.
Reason: All changes in climate and weather take place in the troposphere.
(a) Both assertion and reason are true, and the reason is the correct explanation of the assertion.
(b) Both assertion and reason are true, but the reason is not the correct explanation of the assertion.
(c) Assertion is true, but the reason is false.
(d) Assertion is false, but the reason is true.
Ans: (a)
The assertion is true because the troposphere, being the lowest layer of the atmosphere, contains various particles, including dust and water vapor. The reason is true because all the weather-related phenomena, including changes in climate, occur within the troposphere. The reason provides a correct explanation for the assertion.

Q4: Assertion: Water vapor decreases with altitude.
Reason: Water vapor acts as a blanket, preventing the Earth from becoming too cold or too hot.
(a) Both assertion and reason are true, and the reason is the correct explanation of the assertion.
(b) Both assertion and reason are true, but the reason is not the correct explanation of the assertion.
(c) Assertion is true, but the reason is false.
(d) Assertion is false, but the reason is true.
Ans: (c)
The assertion is true because water vapor decreases with altitude as the atmosphere becomes less dense. However, the reason is false. Water vapor does play a role in regulating temperature, but it does not act as a "blanket" in the way described. Instead, it acts as a greenhouse gas, trapping heat in the lower atmosphere. The reason does not provide an accurate explanation for the assertion.

Q5: Assertion: The ionosphere reflects radio waves back to Earth.
Reason: The ionosphere contains electrically charged particles known as ions.
(a) Both assertion and reason are true, and the reason is the correct explanation of the assertion.
(b) Both assertion and reason are true, but the reason is not the correct explanation of the assertion.
(c) Assertion is true, but the reason is false.
(d) Assertion is false, but the reason is true.
Ans: (a)
The assertion is true because the ionosphere reflects radio waves back to Earth, making long-distance communication possible. The reason is also true because the ionosphere indeed contains electrically charged particles, mainly ions, which are responsible for this reflection of radio waves. The reason accurately explains why the assertion is true.

Very Short Answer Type Questions

Q1: What is the greenhouse effect?
Ans: The greenhouse effect is the process by which certain gases in the Earth's atmosphere trap heat from the sun, warming the planet.

Q2: How does carbon dioxide affect the Earth's temperature?
Ans: Carbon dioxide acts as a greenhouse gas, absorbing and trapping heat in the atmosphere. Increased levels of carbon dioxide lead to a rise in Earth's temperature, contributing to global warming.

Q3: Where is the ozone layer located in the atmosphere?
Ans: The ozone layer is located in the stratosphere, approximately 10 to 50 kilometers above the Earth's surface.

Q4: What is the importance of the troposphere?
Ans: The troposphere is the lowest layer of the atmosphere and is where weather phenomena occur. It is crucial for supporting life on Earth as it contains the oxygen we breathe and regulates temperature.

Q5: What is the tropopause?
Ans: The tropopause is the boundary between the troposphere and the stratosphere. It marks the transition zone where the temperature stops decreasing with altitude and remains relatively constant.

Q6: Why is the stratosphere significant for life on Earth?
Ans: The stratosphere contains the ozone layer, which absorbs harmful ultraviolet (UV) radiation from the sun. This shields living organisms on Earth's surface from excessive UV exposure, protecting them from harmful effects.

Q7: What is the mesopause?
Ans: The mesopause is the boundary between the mesosphere and the thermosphere, located approximately 85 kilometers above the Earth's surface. It is the coldest point in Earth's atmosphere.

Q8: What is the ionosphere, and what is its role?
Ans: The ionosphere is a region in the upper atmosphere where high-energy radiation from the sun ionizes gas molecules, creating ions. It plays a crucial role in radio communications and reflects radio waves back to the Earth's surface.

Q9: How does temperature change with altitude in the mesosphere?
Ans: In the mesosphere, temperature decreases with increasing altitude. It is the layer of the atmosphere where temperatures are the coldest.

Q10: What is the primary source of increased carbon dioxide in the atmosphere?
Ans: The burning of fossil fuels, such as coal, oil, and natural gas, is the primary source of increased carbon dioxide emissions in the Earth's atmosphere.

Short Answer Type Questions

Q1: Describe the composition of the Earth's atmosphere.
Ans: The Earth's atmosphere is composed of various gases. The majority of the atmosphere consists of nitrogen (approximately 78%) and oxygen (about 21%). Other trace gases include argon, carbon dioxide, neon, helium, and methane. Water vapor is also present in varying amounts. Additionally, the atmosphere contains tiny solid and liquid particles, such as dust, aerosols, and pollutants.

Q2: Explain the role of water vapor in maintaining the Earth's temperature.
Ans: Water vapor plays a crucial role in maintaining the Earth's temperature through the greenhouse effect. It acts as a greenhouse gas, trapping heat radiated from the Earth's surface and preventing it from escaping into space. This leads to a warming effect on the planet. Water vapor absorbs and re-emits infrared radiation, creating a balance between incoming solar radiation and outgoing thermal radiation. Without water vapor, the Earth would be much colder, making it uninhabitable.

Q3: Discuss the distribution of dust particles in the atmosphere.
Ans: Dust particles in the atmosphere are distributed unevenly. They originate from various sources, such as wind erosion, volcanic eruptions, and human activities. These particles can vary in size, composition, and concentration. Larger dust particles tend to settle closer to their source, while smaller particles can be transported over long distances by atmospheric circulation. Dust particles can affect air quality, visibility, and climate. They can also act as condensation nuclei for cloud formation and influence atmospheric chemistry.

Q4: Differentiate between the troposphere and the stratosphere in terms of their characteristics.
Ans: The troposphere is the lowest layer of the Earth's atmosphere, extending from the surface up to about 10-15 kilometers. It is characterized by decreasing temperature with increasing altitude and is where weather phenomena occur. The stratosphere lies above the troposphere and extends up to about 50 kilometers. In the stratosphere, the temperature increases with altitude due to the presence of the ozone layer. The stratosphere is relatively stable and contains the highest concentration of ozone, which absorbs harmful ultraviolet (UV) radiation from the Sun.

Q5: What is the significance of the tropopause in the atmosphere?
Ans: The tropopause is a boundary between the troposphere and the stratosphere. Its significance lies in the fact that it acts as a barrier to the exchange of air and pollutants between these two layers. The tropopause is characterized by a stable temperature profile, marking the transition from decreasing temperature in the troposphere to increasing temperature in the stratosphere. It plays a crucial role in maintaining the structure and stability of the Earth's atmosphere.

Q6: Elaborate on the role of the ionosphere and its impact on radio waves.
Ans: The ionosphere is a region in the Earth's atmosphere that contains a high concentration of ions and free electrons. It is located approximately 60-1,000 kilometers above the Earth's surface. The ionosphere plays a significant role in the propagation of radio waves. It reflects and refracts radio waves, allowing long-distance communication by bouncing signals off the ionized layers. Different ionospheric layers can reflect different frequencies of radio waves, enabling the transmission of radio signals over long distances. However, ionospheric conditions can vary with solar activity, affecting the quality and reliability of radio communication.

Q7: Why does the temperature change in the mesosphere as altitude increases?
Ans: In the mesosphere, the temperature decreases with increasing altitude. This temperature change occurs due to the decreasing density of gas molecules and the absorption of solar radiation by ozone molecules. The mesosphere is located above the stratosphere and extends up to about 85 kilometers. It is the coldest layer of the Earth's atmosphere, with temperatures dropping as low as -90 degrees Celsius. The thin air in the mesosphere makes it less efficient at absorbing and retaining heat, resulting in lower temperatures at higher altitudes.

Q8: Explain the consequences of an increase in the volume of carbon dioxide in the atmosphere.
Ans: An increase in the volume of carbon dioxide (CO₂) in the atmosphere leads to several consequences. CO₂ is a greenhouse gas, and higher concentrations contribute to the enhanced greenhouse effect, leading to global warming and climate change. The consequences include rising temperatures, melting glaciers and polar ice caps, sea-level rise, altered weather patterns, increased frequency and intensity of extreme weather events, disruption of ecosystems, and potential threats to human health and livelihoods. Additionally, increased CO₂ in the atmosphere can contribute to ocean acidification, negatively impacting marine life and coral reefs.

Long Answer Type Questions

Q1: Describe the composition of the Earth's atmosphere and its role in climate change.
Ans: The Earth's atmosphere is composed of various gases, including nitrogen (78%), oxygen (21%), argon (0.9%), and trace amounts of carbon dioxide, methane, ozone, water vapor, and other gases. These gases play a crucial role in climate change through the greenhouse effect.
The Role of Greenhouse Gases:
Greenhouse gases, such as carbon dioxide (CO₂), methane (CH₄), and water vapor (H₂O), trap heat in the Earth's atmosphere. They allow sunlight to pass through and warm the planet's surface, but they also prevent some of the heat from escaping back into space. This natural process helps regulate the Earth's temperature, making it habitable.
Impact on Climate Change:
Human activities, such as burning fossil fuels and deforestation, have significantly increased the concentration of greenhouse gases in the atmosphere. This enhanced greenhouse effect leads to global warming and climate change. The increased heat-trapping capacity of these gases contributes to rising temperatures, melting ice caps, sea-level rise, extreme weather events, and shifts in precipitation patterns.

Q2: Discuss the structure of the atmosphere, including its different layers and their characteristics.
Ans: Layers of the Atmosphere: The Earth's atmosphere is divided into five main layers: troposphere, stratosphere, mesosphere, thermosphere, and exosphere.

• Troposphere: The troposphere is the lowest layer and extends from the Earth's surface up to about 8-15 kilometers. It contains almost all of the Earth's weather phenomena and is where we live. Temperature decreases with altitude in this layer.
• Stratosphere: The stratosphere lies above the troposphere and extends up to about 50 kilometers. It contains the ozone layer, which absorbs harmful ultraviolet (UV) radiation from the Sun. Temperature increases with altitude in this layer.
• Mesosphere: The mesosphere is located above the stratosphere and extends up to about 85 kilometers. It is the layer where meteors burn upon entering the Earth's atmosphere. Temperature decreases with altitude in this layer.
• Thermosphere: The thermosphere lies above the mesosphere and extends up to about 600 kilometers. It experiences high temperatures due to the absorption of solar radiation. This is also the layer where the Northern and Southern Lights occur.
• Exosphere: The exosphere is the outermost layer and extends from the thermosphere to space. It consists of a very thin atmosphere that gradually merges with the vacuum of space.

Importance of Understanding Atmospheric Structure:
Understanding the different layers of the atmosphere is crucial for studying weather patterns, climate change, and the behavior of gases. It helps scientists predict and explain phenomena such as temperature variations, air circulation, ozone depletion, and the effects of human activities on the atmosphere.

Q3: Explain the role of water vapor in the atmosphere, its distribution, and its impact on temperature regulation.
Ans: Distribution of Water Vapor:
Water vapor is the gaseous form of water and is present in the Earth's atmosphere. Its distribution varies both spatially and temporally. It is more abundant near water bodies, such as oceans and lakes, and is influenced by factors like temperature, humidity, and air circulation patterns.
Role in Maintaining Temperature:
Water vapor plays a crucial role in regulating the Earth's temperature through the process of evaporation and condensation. When water evaporates, it absorbs heat energy from the surroundings, cooling the environment. This cooling effect is vital for maintaining a stable temperature on Earth.
Importance for Climate and Weather:

• Water vapor is a greenhouse gas, meaning it contributes to the greenhouse effect and influences climate. It absorbs and emits infrared radiation, trapping heat in the atmosphere. As temperatures rise, more water evaporates, leading to increased water vapor in the atmosphere. This amplifies the greenhouse effect, resulting in further warming and climate change.
• Water vapor is also a key factor in weather patterns, as it condenses to form clouds and precipitation. Changes in the distribution and concentration of water vapor can affect the intensity and frequency of rainfall, storms, and other weather events.
  
  

Q4: Analyze the consequences of increased carbon dioxide in the atmosphere, its sources, and its implications for the environment.
Ans: Sources of Increased Carbon Dioxide:
Carbon dioxide (CO₂) is primarily released into the atmosphere through human activities, including the burning of fossil fuels (such as coal, oil, and natural gas), deforestation, and industrial processes. These activities have significantly increased CO₂ levels since the industrial revolution.
Impact on Temperature and Climate:
Increased carbon dioxide in the atmosphere is a major contributor to global warming and climate change. CO₂ is a greenhouse gas that traps heat, leading to the enhanced greenhouse effect. This results in rising global temperatures, melting glaciers and ice caps, sea-level rise, and changes in precipitation patterns.
Environmental Consequences and Solutions:

• The consequences of increased carbon dioxide are far-reaching. It leads to more frequent and intense heatwaves, droughts, wildfires, and extreme weather events. It also affects ecosystems, causing shifts in species distribution, loss of biodiversity, and disruption of natural cycles.
• To mitigate the impacts, reducing carbon dioxide emissions is crucial. This can be achieved through transitioning to renewable energy sources, improving energy efficiency, promoting afforestation, and implementing sustainable practices. International agreements, such as the Paris Agreement, aim to limit global warming by reducing greenhouse gas emissions and promoting climate resilience.