The correct option is 1 only
Explanation
The exosphere is the uppermost layer of the Earth's atmosphere. It lies above the thermosphere and represents the transition zone between the Earth's atmosphere and interplanetary space.
Statement-wise Analysis
- Statement 1 is Correct: The exosphere is the highest and outermost layer of the atmosphere. It extends from the top of the thermosphere (approximately 600-700 km altitude) up to 10,000 km.
- Statement 2 is Incorrect: The exosphere does not have a distinct upper boundary. Instead, it gradually merges into outer space. The magnetopause is the boundary of the Earth's magnetosphere, where the Earth's magnetic field meets the solar wind, but it is not defined as a distinct physical barrier separating the atmospheric exosphere from space.
- Statement 3 is Incorrect: The exosphere contains extremely rarefied air, meaning the density of gases is very low. It is composed mainly of light gases such as hydrogen and helium, rather than dense gases. The particles are so sparse that they can travel hundreds of kilometers without colliding with one another.
Key Takeaway
The exosphere is the outermost layer of the atmosphere, characterized by extremely low density and light gases (hydrogen and helium), and it gradually fades into outer space without a sharp boundary.