Previous Year Question
Arrange the following atmospheric zones in terms of the distance from the earth's surface in increasing order and select the correct answer from the code given below:
Thermosphere
Troposphere
Stratosphere
Mesosphere
Codes:
1, 3, 4, 2
2, 3, 1, 4
3, 4, 2, 1
2, 3, 4, 1
Correct Answer: D
Detailed Solution
The Earth's Atmosphere is a mixture of different gases divided into several layers based on temperature variations and altitude. Their order from the Earth's surface upward is Troposphere → Stratosphere → Mesosphere → Thermosphere → Exosphere. Each layer has distinct altitudinal ranges, temperature characteristics, and physical properties. Atmospheric boundaries are not fixed and may vary with latitude, season, and solar activity.
The Troposphere is the lowest atmospheric layer, generally extending from the Earth's surface to approximately 8–18 kilometres. Most of the atmospheric mass and nearly all atmospheric water vapour are concentrated in this layer. Clouds, rainfall, storms, and other major weather phenomena occur here. Its upper boundary is called the Tropopause. Above it, the Stratosphere extends to approximately 50 kilometres. This layer contains the Ozone Layer, which absorbs Ultraviolet Radiation from the Sun. Consequently, temperature generally increases with altitude in the Stratosphere.
The Mesosphere lies above the Stratosphere and extends from approximately 50 to 85 kilometres. Temperature decreases with increasing altitude in this layer, and most Meteors burn up while entering the atmosphere. Above it, the Thermosphere extends from approximately 85 to 600 kilometres. Temperatures can increase significantly because of the absorption of high-energy ultraviolet radiation and X-rays from the Sun. A major portion of the Ionosphere lies within the Thermosphere, influencing radio communications and phenomena such as Auroras. Above the Thermosphere lies the Exosphere, which gradually merges into outer space.