Class 11 Geography - RAJASTHAN
Composition and Structure of Atmosphere
The chapter 'Composition and Structure of Atmosphere' in Class 11 Geography for Rajasthan Board (RBSE) explores the envelope of air surrounding the Earth. Students learn about the various gases, water vapour, and dust particles that make up the atmospheric composition. It details the five distinct layers of the atmosphere—troposphere, stratosphere, mesosphere, thermosphere, and exosphere—based on temperature variations with height. Understanding this chapter is crucial for board exams as it forms the fundamental basis for climatology, weather patterns, and global climate change, frequently appearing in short-answer and map-based questions.
Start Learning FreeKey Concepts
Composition of the Atmosphere
The atmosphere is made up of gases, water vapour, and dust particles, with Nitrogen (78%) and Oxygen (21%) being the two primary permanent gases.
Structure of the Atmosphere
The atmosphere is divided into five vertical layers based on temperature conditions: Troposphere, Stratosphere, Mesosphere, Thermosphere, and Exosphere.
Troposphere
The lowest and densest layer of the atmosphere where all weather phenomena occur, and temperature decreases with an increase in height (normal lapse rate).
Stratosphere
The layer above the troposphere that contains the ozone layer, which absorbs harmful ultraviolet rays, making temperatures increase with height.
Insolation and Temperature Lapse Rate
The rate at which temperature decreases with an increase in altitude in the troposphere, averaging 6.5°C per 1,000 meters.
Important Formulas
Board Exam Info
In Rajasthan Board (RBSE) Class 11 Geography exams, this chapter typically carries around 4 to 6 marks. Questions usually include objective type/multiple choice questions, very short answers defining specific layers or gases, and short descriptive questions explaining the structure of the atmosphere with a labelled diagram.
Frequently Asked Questions
Why does temperature decrease with height in the troposphere?
The troposphere is heated from below by the Earth's surface (terrestrial radiation) rather than directly by the Sun, so air farther from the surface is cooler.
What is the importance of the ozone layer in the stratosphere?
The ozone layer absorbs harmful ultraviolet (UV) radiation from the Sun, protecting life on Earth from skin cancer and other severe health hazards.
Why are dust particles important in the atmosphere?
Dust particles act as hygroscopic nuclei around which water vapour condenses to form clouds, fog, and precipitation, and they also cause the red and orange colours during sunrise and sunset.
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