Correct Option
The correct option is It absorbs UV rays..
Explanation
Ozone ($O_3$) is a chemically active, triatomic form of oxygen present in the Earth's atmosphere. It plays a critical role in the Earth's radiation balance, acting differently depending on its altitude.
Statement-wise Analysis
- Statement It is found in the Troposphere only. is Incorrect: Ozone is not confined to the Troposphere. Approximately 90% of atmospheric ozone is concentrated in the Stratosphere (specifically between 15 and 35 km), forming the "Ozone Layer." The remaining 10% is found in the Troposphere, where it acts as a pollutant.
- Statement It absorbs UV rays. is Correct: The fundamental significance of stratospheric ozone is its ability to absorb harmful solar Ultraviolet (UV) radiation. This absorption protects life on Earth from the damaging effects of UV rays and is responsible for the increase in temperature with height in the stratosphere.
- Statement It is transparent to terrestrial radiation. is Incorrect: Ozone is not transparent to terrestrial radiation. It is a potent Greenhouse Gas (GHG) that absorbs outgoing longwave terrestrial radiation, thereby trapping heat in the atmosphere.
- Statement It is the most abundant gas. is Incorrect: Ozone is a trace gas found in very small quantities. The most abundant gas in the atmosphere is Nitrogen (78.08%), followed by Oxygen (20.95%) and Argon (0.93%).
Key Takeaway: Stratospheric ozone ("good ozone") shields the Earth from UV radiation, whereas tropospheric ozone ("bad ozone") acts as a pollutant and a greenhouse gas by absorbing terrestrial radiation.