The ozone layer acts as Earth’s natural shield against harmful ultraviolet (UV) radiation from the Sun, particularly UV-B and UV-C, which are most damaging to living organisms.
Structure and Location:
- The ozone layer is found in the stratosphere, approximately 15–35 km above Earth’s surface.
- It consists of ozone (O₃) molecules, formed when UV radiation splits O₂ molecules, and the free oxygen atoms combine with other O₂ to form O₃.
How It Protects Us:
1. Absorption of UV-C (100–280 nm)
- UV-C is the most energetic and highly dangerous form of UV radiation.
- The ozone layer absorbs almost 100% of UV-C, preventing it from reaching Earth’s surface.
2. Absorption of Most UV-B (280–315 nm)
- UV-B causes sunburn, skin cancer, eye damage, and harms plants and animals.
- The ozone layer absorbs about 90% of UV-B, allowing only a small amount to reach the ground.
3. Minimal Effect on UV-A (315–400 nm)
- UV-A is less harmful and mostly passes through the ozone layer.
- It penetrates deeper into the skin and contributes to aging and long-term skin damage, but is less energetic than UV-B or UV-C.
Consequences of Ozone Depletion:
- Thinning of the ozone layer (e.g., the ozone hole) allows more UV-B to reach the Earth.
- This leads to higher rates of skin cancer, cataracts, and immune suppression in humans, and can damage crops, phytoplankton, and ecosystems.