The correct option is 1 only
Explanation
The atmosphere is a mixture of different gases that surrounds the Earth. It is held in place by the Earth's gravitational pull and is integral to the existence of life. The density and composition of the atmosphere vary significantly with altitude.
Statement-wise Analysis
- Statement 1 is Correct: Air is a mixture of gases, primarily Nitrogen (78%) and Oxygen (21%). In its pure form, air is colourless, odourless, and tasteless. It becomes visible or odorous only when pollutants, dust, or specific volatile compounds are present in significant quantities.
- Statement 2 is Incorrect: The atmosphere is not uniformly distributed. Due to gravity, the gases are compressed near the surface. Approximately 99% of the total mass of the atmosphere is confined to the height of 32 km from the Earth's surface. The air becomes extremely rarefied (thin) at higher altitudes, and very little mass exists above 100 km.
- Statement 3 is Incorrect: The atmosphere is a continuous envelope of gases that surrounds the entire Earth, from the equator to the poles. It is not restricted to any specific latitudinal zone. While the thickness (height) of the troposphere varies between the equator and poles, the atmosphere itself exists globally.
Key Takeaway: The atmosphere is densest near the Earth's surface due to gravity, with 99% of its total mass situated within the first 32 km of altitude.