Previous Year Question

About 90% of the Ozone present in Earth's atmosphere occurs in the Stratosphere. For this reason, the ozone-rich region of the Stratosphere is commonly known as the Ozone Layer.

The Stratosphere is the atmospheric layer situated above the Troposphere. Ozone is formed here through photochemical reactions involving Ultraviolet (UV) radiation from the Sun. UV radiation can first split molecular Oxygen O₂ into Oxygen atoms. These Oxygen atoms then combine with other O₂ molecules to form Ozone O₃.

This Stratospheric Ozone is environmentally extremely important because it absorbs a large proportion of harmful solar Ultraviolet radiation, particularly UV-B, thereby helping to protect life on Earth.

Some Ozone is also present in the Troposphere, but its amount is much smaller. Ground-level or Tropospheric Ozone can also act as a secondary air pollutant and can be harmful to human health and vegetation.

The Mesosphere lies above the Stratosphere and Ozone concentration becomes much lower there, while the Exosphere is the extremely rarefied outermost region of the atmosphere and does not contain the maximum concentration of Ozone.