The correct option is 2 only
Explanation
The Troposphere is the lowermost layer of the atmosphere. It is the most important layer for all biological activity and weather phenomena. The height of this layer varies significantly depending on latitude and season.
Statement-wise Analysis
- Statement 1 is Incorrect: The thickness of the troposphere is greatest at the equator because heat is transported to great heights by strong convectional currents. Its height is approximately 18 km at the equator and roughly 8 km near the poles.
- Statement 2 is Correct: In the troposphere, temperature decreases with an increase in height. This rate of decrease is known as the Normal Lapse Rate, which is approximately 6.5°C for every 1000 meters of ascent. The temperature increases with height in the Stratosphere and Thermosphere, not the Troposphere.
- Statement 3 is Incorrect: The troposphere is not devoid of dust particles and water vapour. In fact, it contains the vast majority of the atmosphere's water vapour and aerosols (dust, pollen, etc.). Consequently, all weather changes-such as cloud formation, rainfall, and storms-occur exclusively in this layer.
Key Takeaway
The Troposphere is characterized by a decrease in temperature with altitude (Normal Lapse Rate), contains almost all atmospheric water vapour and dust, and exhibits variable thickness (highest at the equator, lowest at the poles).