Class 11 Geography - BIHAR
Composition and Structure of Atmosphere
The chapter 'Composition and Structure of Atmosphere' in Class 11 Geography explores the gaseous envelope surrounding the Earth. Students learn about permanent and variable gases like nitrogen, oxygen, and carbon dioxide, as well as dust particles and water vapour. The chapter details the five atmospheric layers: Troposphere, Stratosphere, Mesosphere, Thermosphere, and Exosphere, based on temperature variations. Understanding this chapter is crucial for BSEB board exams as it forms the foundational base for climatology, explaining weather phenomena, climate change, and how the atmosphere protects life on Earth by absorbing harmful solar radiation.
Start Learning FreeKey Concepts
Composition of the Atmosphere
The atmosphere is made up of gases, water vapour, and dust particles. Nitrogen (78.08%) and Oxygen (20.95%) make up the bulk of permanent gases.
Greenhouse Gases
Gases like carbon dioxide, ozone, methane, and water vapour are transparent to incoming solar radiation but opaque to outgoing terrestrial radiation, trapping heat.
Troposphere
The lowest layer of the atmosphere where all weather changes occur, and temperature decreases with increasing height at the normal lapse rate.
Stratosphere
The layer above the troposphere containing the ozone layer, which absorbs harmful ultraviolet rays and prevents them from reaching the Earth's surface.
Ionosphere
Located within the thermosphere, this layer contains electrically charged ions that reflect radio waves back to the Earth, enabling wireless communication.
Important Formulas
Board Exam Info
In the Bihar (BSEB) Class 11 Geography examinations, this chapter typically carries around 4 to 6 marks. Common question types include short answer questions on the layers of the atmosphere, very short objective questions regarding gas percentages, and long-answer questions detailing the structure of the atmosphere with a neat diagram.
Frequently Asked Questions
Why does temperature decrease with height in the troposphere?
The troposphere is heated from below by the Earth's surface rather than directly by the sun. As you move higher away from the heat source (the surface), the air becomes colder.
What is the difference between composition and structure of the atmosphere?
Composition refers to the types of gases, dust, and water vapour that make up the air, while structure refers to the vertical layers of the atmosphere divided based on temperature changes.
Why is the ozone layer important for life on Earth?
The ozone layer present in the stratosphere absorbs harmful ultraviolet (UV) radiation coming from the sun, protecting living organisms from skin cancer, eye damage, and genetic mutations.
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