Short Question Answers : Composition and Structure of Atmosphere | Geography Class 11 - Humanities/Arts PDF Download

Q1. What is atmosphere?
Ans: The atmosphere is an envelope of gases surrounding the Earth. It plays a crucial role in supporting life by providing essential elements and regulating temperature.

• Composed mainly of nitrogen (78%) and oxygen (21%).
• Contains trace amounts of other gases, including carbon dioxide and argon.
• Acts as a protective layer, filtering harmful solar radiation.
• Facilitates weather patterns and climate.

Q2. Which are the two major gases constituting the atmosphere?
Ans: Nitrogen and oxygen are the two main gases that make up the atmosphere. They play crucial roles in supporting life on Earth.

• Nitrogen constitutes about 78% of the atmosphere.
• Oxygen makes up around 21% of the atmosphere.

These gases are essential for various biological and chemical processes, including respiration and combustion.

Q3. What is the percentage of nitrogen gas present in the atmosphere?
Ans: The atmosphere contains approximately 78% of nitrogen gas. This makes nitrogen the most abundant gas in the atmosphere.

Q4. What is the percentage of oxygen gas present in the atmosphere?
Ans: The atmosphere contains approximately 21% of oxygen gas. This percentage is crucial for supporting life on Earth.

Q5. Why is the atmosphere held to the Earth?
Ans: The atmosphere is held to the Earth primarily due to the force of gravity. This gravitational pull ensures that the gases surrounding our planet remain close to its surface.

Q6. Name two gases found in the upper layers of the atmosphere.
Ans: Argon and Helium are two gases found in the upper layers of the atmosphere.

Q7. Which rays are absorbed by ozone gas?
Ans: The ozone layer plays a crucial role in protecting life on Earth by absorbing:

• Ultra-violet rays emitted by the sun.

This absorption prevents these harmful rays from reaching the surface, thereby safeguarding living organisms.

Q8. Which is the weather-making layer of the atmosphere?
Ans: Troposphere.

• The troposphere is the lowest layer of the atmosphere.
• It is where all weather occurs.
• Its average height is about 13 km, varying from 8 km at the poles to 18 km at the equator.
• This layer contains dust and water vapour.
• Temperature decreases by approximately 1°C for every 165 m of height.
• It is crucial for all biological activity.

Q9. What is the normal lapse rate of temperature?
Ans: The normal lapse rate of temperature is 1°C for every 165 metres of altitude. This means that as you ascend in the atmosphere, the temperature typically decreases by this amount.

Q10. What is the use of the ionosphere?
Ans: The ionosphere plays a crucial role in communication and navigation by:

• Reflecting radio waves back to Earth.
• Facilitating long-distance radio communication.
• Enabling GPS signals to reach devices.

This layer is essential for various technologies that rely on radio frequencies.

Q11. What is the function of dust particles in the atmosphere?
Ans: Dust particles in the atmosphere play several important roles:

• They contribute to the formation of fog and clouds.
• They absorb insolation from the sun.
• They act as hygroscopic nuclei, around which water vapour condenses.

Dust particles are typically found in the lower layers of the atmosphere but can be lifted to higher altitudes by convectional air currents. Their concentration is higher in subtropical and temperate regions due to dry winds.

Q12. Name the science which studies atmospheric conditions.
Ans: Meteorology is the science that studies atmospheric conditions.

• Atmosphere: The layer of gases surrounding Earth, essential for life.
• Elements of Weather and Climate: Key factors include temperature, pressure, winds, humidity, clouds, and precipitation.
• Composition of Atmosphere: Mainly consists of nitrogen (78%), oxygen (21%), and trace gases.
• Importance of Troposphere: It is the lowest layer, where weather occurs and contains most of the atmosphere's mass.

Q13. Name the main elements of the atmosphere.
Ans: The main elements of the atmosphere include:

• Gases
• Dust particles
• Water vapour

Q14. Name the different layers of the atmosphere.
Ans: 

• Troposphere – the lowest layer, where weather occurs, extending up to about 13 km.
• Stratosphere – above the troposphere, reaching up to 50 km, containing the ozone layer that absorbs harmful UV radiation.
• Mesosphere – extends from 50 km to 80 km, where temperatures decrease with altitude.
• Ionosphere – located between 80 km and 400 km, filled with charged particles that reflect radio waves.
• Exosphere – the uppermost layer, gradually merging with outer space, containing very few particles.

Q15. Define the climate of a place. How do you determine it?
Ans: Climate refers to the average weather conditions of a place over a long period, typically 30 to 40 years. It represents a consistent pattern, unlike daily weather, which can vary significantly.

• The climate is the long-term average of weather.
• It remains relatively stable year after year.
• Data from the past few decades is used to determine climate.

Q16. Name the elements of weather.
Ans: The elements of weather are the atmospheric conditions that define the weather in a specific area. They include:

• Temperature
• Pressure
• Winds
• Sunshine
• Humidity
• Cloudiness
• Rainfall
• Mist and fog

Q17. Name the major controls of climate.
Ans: The major factors that influence climate variations across different regions are known as the elements of climate. These include:

• Latitude
• Altitude
• Distribution of land and water
• Pressure
• Prevailing winds
• Ocean currents
• Mountain barriers

Q18. ‘Water vapour acts like a Blanket.’ Discuss.
Ans: Water vapour decreases from the equator to the poles. It plays a crucial role by:

• Absorbing some of the sun's insolation reduces the amount that reaches the Earth's surface.
• Retaining the Earth's radiated heat helps to maintain a stable temperature.
• Influencing air stability and instability.

Overall, water vapour acts like a blanket, preventing the Earth from becoming too cold or too hot.

Q19. Explain the importance of ozone gas.
Ans: The ozone layer is located between 10 and 50 km above the Earth's surface. Its significance includes:

• It acts as a filter, absorbing harmful ultraviolet (UV) rays from the sun.
• By preventing these rays from reaching the Earth, it shields life from intense energy that can cause damage.
• This protective function is essential for maintaining a safe environment for all living organisms.

Q20. Explain the significance of atmosphere to man.
Ans: Significance of Atmosphere to Man

• The atmosphere makes the Earth habitable.
• It contains essential gases like oxygen and nitrogen, vital for plant and animal life.
• It holds water vapour, which leads to precipitation.
• It protects us from numerous falling meteors.
• It absorbs harmful ultraviolet rays.
• It moderates temperature, acting as a natural air conditioner.

Q21. Write a note on the ozone layer of the atmosphere. Why is it depleting? Where has been a hole in this layer found? What are its harmful effects?
Ans: Ozone Layer

The ozone layer is a thick layer of ozone gas located in the upper atmosphere. It plays a crucial role by absorbing harmful ultraviolet (UV) rays from the sun.

• The depletion of the ozone layer is primarily caused by:
  • Excessive use of certain chemicals and carbons that react with ozone.
  • Atomic explosions.
• A significant hole in the ozone layer was discovered over Antarctica in 1980.
• Through this hole, increased UV rays can reach the Earth, leading to:
  • Higher risks of skin cancer.
  • Potential for blindness.

Q22. Name the main constituents of the pure dry air.
Ans: The atmosphere is primarily made up of:

• Gases
• Water vapour
• Dust particles

About 99% of the atmosphere consists of two main gases:

• Nitrogen - 78%
• Oxygen - 21%

The remaining 1% includes various gases such as:

• Hydrogen
• Argon
• Ozone
• Helium
• Carbon dioxide

Q23. Define Atmosphere.
Ans: The atmosphere is a vast layer of air surrounding the Earth. It is held in place by gravity and is essential for life. Key points include:

• It consists of various gases, including oxygen and carbon dioxide.
• It supports all living organisms by providing necessary air.
• About 99% of the atmosphere's mass is within 32 km of the Earth's surface.

The atmosphere is crucial for human survival and the health of our planet.

Q24. What is tropopause?
Ans: Tropopause is the boundary that separates the stratosphere from the troposphere. It is often referred to as the "ceiling of the troposphere" because it marks the upper limit of this layer.

Key features of the tropopause include:

• It acts as a thin transitional zone between the troposphere and stratosphere.
• The temperature at the tropopause is approximately -80°C over the equator and around -45°C at the poles.
• Temperature remains nearly constant at this altitude.

Q25. Why is the troposphere considered to be the most significant layer of the atmosphere?
Ans: The troposphere is the most significant layer of the atmosphere for several reasons:

• This layer is responsible for weather formation.
• All weather-related processes occur within this layer.
• It exhibits great contrasts in climate and weather due to temperature variations.
• Most of the water vapour is found here, leading to condensation, cloud formation, and precipitation.
• Dust particles contribute to phenomena like fog, clouds, and smog.
• Convection currents, essential for heating and cooling, are confined to this layer.
• The air in the troposphere is unstable, causing atmospheric disturbances such as storms and cyclones.