Class 11 Geography - HARYANA
Composition and Structure of Atmosphere
This chapter explores the composition and vertical structure of Earth's atmosphere, which is vital for Class 11 Haryana Board (BSEH) students. You will study the gases, water vapour, and dust particles that make up the air around us, and how the atmosphere is divided into five distinct layers—Troposphere, Stratosphere, Mesosphere, Thermosphere, and Exosphere—based on temperature variations. Understanding this chapter is essential because it forms the physical foundation for later topics like weather, climate, and global warming. Board exams frequently test your ability to draw and label atmospheric layers and explain phenomena like the lapse rate.
Start Learning FreeKey Concepts
Composition of Atmosphere
The atmosphere is made up of permanent gases like nitrogen (78%) and oxygen (21%), along with variable gases like carbon dioxide, water vapour, and dust particles.
Structure of Atmosphere
The atmosphere is divided into five concentric layers based on temperature changes: Troposphere, Stratosphere, Mesosphere, Thermosphere, and Exosphere.
Troposphere
The lowest and densest layer of the atmosphere where all weather phenomena occur, experiencing a decrease in temperature with height at the normal lapse rate.
Stratosphere
The layer above the troposphere containing the ozone layer, which absorbs harmful ultraviolet radiation and causes temperatures to increase with altitude.
Normal Lapse Rate
The rate at which temperature decreases with an increase in elevation in the troposphere, which is roughly 6.4 degrees Celsius per 1,000 meters.
Important Formulas
Board Exam Info
In the Haryana Board (BSEH) Class 11 Geography exams, this chapter typically carries around 4 to 6 marks. Questions usually include very short answer questions (1 mark), short answer questions (3 marks) defining specific layers or the composition, and sometimes a 5-mark question asking you to draw a well-labelled diagram of the structure of the atmosphere with temperature variations.
Frequently Asked Questions
Why does temperature decrease with height in the troposphere?
Temperature decreases because the troposphere is heated from below by the Earth's surface, which absorbs solar radiation and radiates it back into the lower atmosphere.
What is the ozone layer and in which layer is it found?
The ozone layer is a region of high ozone concentration that absorbs harmful UV rays from the Sun; it is primarily found in the stratosphere.
Why do meteors burn up in the mesosphere?
Meteors burn up in the mesosphere because the air density, though low, is sufficient to create friction and extreme heat against fast-moving space rocks.
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