Important Questions: Composition & Structure of Atmosphere | Geography Class 11 - Humanities/Arts PDF Download

Very Short Answer Type Questions

Q1: What is heterosphere?
Ans: The layer of the atmosphere 90 km above the surface of the earth where the composition begins to change with a progressive increase in the lighter gases, is called heterosphere.

Q2: Which gas of the atmosphere does not take part in a chemical reaction?
Ans: ‘Argon’ does not take part in a chemical reaction.

Q3: Which gas despite its small percentage is crucial in atmospheric processes?
Ans: Carbon dioxide is an important gas in the atmospheric processes.

Q4: What energises the atmosphere?
Ans: The atmosphere is energised by the sun.

Q5: Name two broad layers of the atmosphere.
Ans: Homosphere and heterosphere are two broad layers of the atmosphere.

Q7: What is wind?
Ans: The horizontal motion of the air is known as wind.

Q8: Which gas acts as a filter and protects us from ultraviolet rays?
Ans: Ozone gas protects us from ultraviolet rays and acts as a filter.

Short Answer Type Questions

Q9: What is meant by a normal lapse rate?
Ans: The temperature decreases with altitude because the atmosphere is heated more by the heat radiated from the earth’s surface. Wanner air lying under the cooler air goes up or turns downward. In this layer, the temperature decreases vertically at a rate of 0.65°C per 100 metres. It is called the normal lapse rate.

Q10: Name the gases and other materials which compose the atmosphere.
Ans: Nitrogen, oxygen and argon are the most important gases of the atmosphere. In addition, it contains gases like carbon dioxide, neon, helium, ozone, hydrogen, methane, krypton and xenon. Besides, there are also present huge amounts of solid and liquid particles collectively called aerosols.

Q11: What is the importance of carbon dioxide on the earth?
Ans: By volume carbon dioxide constitutes 0.03% of the total gases of the earth’s atmosphere. Although it forms a small portion, it is an important gas in the atmospheric processes. It can absorb the heat and thus allows the lower atmosphere to be warmed up by heat radiation coming from the sun and from the earth’s surface. Green plants in the process of photosynthesis utilise carbon dioxide from the atmosphere.

Q12: Identify the climatic controls.
Ans: The various climatic controls are given below :

• Latitude or sun.
• Distribution of land and water
• The great semi-permanent high and low-pressure belts
• Winds
• Altitude
• Mountain barriers
• Ocean currents
• Storms of various kinds

Q13: What are the main characteristics of the lowermost layer of the atmosphere?
Ans: The lowermost layer is the troposphere.

• Its average height is 16-18 km.
• All biological activities occur in this layer.
• All the atmospheric processes take place in this layer.
• It is 16 km thick at the equator and 10 km thick at the poles.

Long Answer Type Questions

Q14: What is the difference between condensation and precipitation?
Ans: Condensation is the physical process of the transition of a substance from the vapour to the liquid state, e.g., as a result of cooling or increase of pressure. It occurs in the atmosphere when the air is saturated or when it is cool. Thus, the change of state of the moisture from invisible water vapour to visible liquid (water) or solid (ice or snow ) state is known n as condensation. It is opposite of evaporation.
Precipitation, on the other hand, means ‘throwing down of moisture’. Continuous condensation in the body of the air helps the water droplets to grow in size so that the resistance of the air fails to keep them suspended. In such cases, only an ascending air current can keep them floating in the air. In the absence of such a current, the products of condensation begin to fall on the earth’s surface. The process whereby the water vapour first condenses in the air and then falls on to the earth is called precipitation.

Q15: Define the atmosphere. Explain its importance to human life.
Ans: The atmosphere is a mixture of air and various gases which envelopes the earth all around. It represents the gaseous realm of the earth. It is held to the earth by the force of gravity.
Importance of atmosphere:

• It contains gases like oxygen (essential for breathing) for man and animals and carbon dioxide for plants.
• By trapping the heat, it acts as a greenhouse. It keeps the earth
• warm.
• One of its layer, the ionosphere, reflects radio waves back to the earth and makes radio communication possible.
• It protects us from the deadly cosmic rays and meteors which are continuously showered on the earth from outer space.
• All the weather phenomenon take place in the atmosphere. Presence of water vapour in the atmosphere brings many changes such as condensation and precipitation. These processes influence the human life, plants and animals.
• It absorbs ultraviolet rays.
• It acts as an air conditioner by moderating the extremes of heat ‘ and cold.
• It is a storehouse of water vapour.

Q16: Distinguish between troposphere and stratosphere.
Ans: The troposphere and the stratosphere are two distinct layers of Earth's atmosphere, each with unique characteristics and functions:

Troposphere:

• Location: The troposphere is the lowest layer of Earth's atmosphere, extending from the Earth's surface up to an average altitude of about 8 to 15 kilometers (5 to 9 miles) above sea level, depending on the location and season.
• Temperature: In the troposphere, the temperature generally decreases with increasing altitude. The boundary between the troposphere and the stratosphere, known as the tropopause, is characterized by this temperature inversion.
• Weather and Air Movement: Virtually all weather events, including clouds, precipitation, storms, and winds, occur in the troposphere. It is the layer where most of Earth's weather phenomena and atmospheric circulation patterns, such as trade winds and jet streams, take place.
• Life and Air Composition: The troposphere contains the air we breathe and supports life on Earth. It contains approximately 75% of the atmosphere's mass and the majority of its water vapor and aerosols.

Stratosphere:

• Location: The stratosphere is situated above the troposphere and extends from the tropopause to an altitude of approximately 50 kilometers (31 miles) above the Earth's surface.
• Temperature: In the stratosphere, the temperature generally increases with altitude due to the presence of the ozone layer. The ozone layer absorbs and scatters ultraviolet solar radiation, which leads to the temperature inversion in this layer.
• Ozone Layer: The stratosphere contains the ozone layer, which is a region with a higher concentration of ozone molecules (O3). The ozone layer plays a crucial role in protecting life on Earth by absorbing most of the Sun's harmful ultraviolet (UV) radiation.
• Jet Streams and Commercial Air Travel: The stratosphere contains the jet streams, which are high-altitude, fast-flowing air currents. Commercial jet aircraft often fly within the lower stratosphere to take advantage of these jet streams, allowing for faster travel times.

Q17: Discuss the principal elements of weather and climate and the major climatic controls.
Ans: The principal elements of weather and climate are temperature precipitation, moisture, pressure and winds. These are called elements because they are the ingredients out of which various weather and climate types are compounded. The temperature and precipitation are the main basic elements to which pressure, winds and other elements are related.
Temperature expresses the intensity of heat. Practically all the heat energy on the earth is the result of insulation or the increasing solar radiation. Unequal distribution of temperature over the earth’s surface causes differences in atmospheric pressure, which causes winds. Higher the temperature, the greater is the capacity’ of air to hold moisture on cooling. The air is not able to retain all the moisture it gathers while warm. This leads to condensation and precipitation. Thus, the temperature is the basic element on which other elements of climate depend.
The climatic controls are :

• Latitude (or sun), distribution of land and water, the great semi¬permanent high and low-pressure belts, winds, altitude, mountain barriers, ocean currents and storms of various kinds.

Q18: What is tropopause?
Ans: The tropopause is the boundary between the troposphere and the stratosphere, two distinct layers of Earth's atmosphere. It is characterized by a temperature inversion, meaning that the temperature in the tropopause stops decreasing with altitude and, in fact, starts to increase. This temperature inversion is a defining feature that separates the troposphere, where temperature generally decreases with altitude, from the stratosphere, where temperature increases with altitude due to the presence of the ozone layer.

In the tropopause:

• Temperature Inversion: As you move higher in the troposphere, the temperature usually decreases. However, when you reach the tropopause, this trend stops, and the temperature either remains constant or starts to increase with altitude. This change in temperature gradient is due to the presence of the ozone layer in the stratosphere.
• Height Variation: The height of the tropopause is not fixed and varies with factors like latitude and season. On average, it is located around 8 to 15 kilometers (5 to 9 miles) above sea level. In the tropics, where the troposphere is higher, the tropopause is found at higher altitudes. In polar regions, where the troposphere is lower, the tropopause is at lower altitudes.
• Weather Features: The tropopause often marks the upper limit of large weather systems, such as thunderstorms and cyclones, which are confined to the troposphere. Above the tropopause, the stratosphere is relatively stable, with less turbulent weather conditions.
• Aircraft Flight: Commercial aircraft typically fly within the lower stratosphere, just below the tropopause, to take advantage of the stable conditions and to avoid the turbulence often experienced in the lower troposphere.

The presence of the tropopause is significant for atmospheric scientists, meteorologists, and pilots because it marks the transition between the two main atmospheric layers with distinct temperature and composition characteristics.

Q19: What is the importance of the atmosphere for the earth?
Ans: The atmosphere is vital for Earth's sustenance as it provides the air we breathe, essential for all life forms. It regulates the planet's temperature through the greenhouse effect, preventing extreme heat during the day and cold at night. The atmosphere shields Earth from harmful solar radiation, including ultraviolet rays, by containing the ozone layer, crucial for life's protection. It also facilitates the water cycle, enabling precipitation and supporting agriculture. Moreover, atmospheric circulation patterns drive weather systems, distributing heat and moisture around the globe. Additionally, the atmosphere plays a fundamental role in Earth's climate, ocean currents, and biodiversity, making it indispensable for the planet's ecological balance and overall well-being.

Q20: Explain the difference between weather and climate.
Ans: Weather and climate are related concepts but refer to different phenomena:

Weather:

• Definition: Weather refers to the atmospheric conditions in a specific place at a specific time. It includes short-term variations in temperature, humidity, precipitation, wind speed, and atmospheric pressure.
• Duration: Weather can change from hour to hour and day to day. It is what we experience on a daily basis, such as sunny or rainy days, hot or cold temperatures, and stormy or calm conditions.
• Prediction: Weather forecasts are short-term predictions about the atmospheric conditions over the next few hours or days. Meteorologists use various tools and technologies to make these forecasts.

Climate:

• Definition: Climate refers to the long-term average of weather patterns in a specific region over a much longer period, usually 30 years or more. It represents the typical weather conditions, including average temperature, precipitation, humidity, and wind patterns, observed over an extended period.
• Duration: Climate encompasses long-term trends and patterns in weather and is relatively stable over extended periods, reflecting the average weather conditions expected in a particular area.
• Variability: While weather can change rapidly, climate describes the typical weather patterns that persist over a long time, allowing scientists to identify trends and variations in temperature and precipitation over decades or centuries.