Which layer contains ozone that protects against UV radiation?

• A. Troposphere
• B. Stratosphere
• C. Mesosphere
• D. Exosphere

Answer: (B)

Ozone that protects against UV radiation is found in the stratosphere. In this layer, UV light drives the formation of ozone from oxygen molecules, creating a relatively concentrated ozone layer roughly 10 to 50 kilometers above the Earth's surface. This ozone absorbs much of the Sun’s ultraviolet radiation, especially UV-B and UV-C, preventing most of it from reaching the surface. The troposphere contains some ozone but is dominated by weather and life-supporting gases, and the ozone there is not the protective shield; it can be harmful at ground level. The mesosphere and exosphere have much less ozone and aren’t where the protective layer resides. So the stratosphere is the layer containing the ozone that shields us from UV radiation.