Ozone filters ultraviolet (UV) radiation primarily by absorbing UV energy, which breaks down the ozone molecule and prevents this harmful radiation from reaching the Earth's surface.
The Core Mechanism: Absorption
The process by which ozone filters UV light, specifically UV-B radiation, is a chemical one involving absorption and molecular change.
- Absorption: An ozone molecule (O₃) in the stratosphere encounters a photon of UV-B radiation.
- Dissociation: The ozone molecule absorbs the energy from the UV-B photon. According to scientific understanding, when an ozone molecule absorbs UV-B, it comes apart into an oxygen molecule (O₂) and a separate oxygen atom (O).
- Reformation: Later, the two components can reform the ozone molecule (O₃). This cycle of breaking apart and reforming allows a single ozone molecule to absorb many UV photons over time.
This continuous process in the ozone layer, located primarily in the stratosphere, acts as a natural shield.
Focusing on UV-B
While ozone absorbs some UV-A and UV-C radiation, it is particularly effective at absorbing most UV-B radiation. UV radiation is categorized into three main types:
- UV-A: Longest wavelength, mostly passes through the ozone layer. Contributes to skin aging.
- UV-B: Medium wavelength, largely absorbed by the ozone layer. Causes sunburn and can damage DNA.
- UV-C: Shortest wavelength, most energetic. Completely absorbed by the ozone layer and atmosphere before reaching the surface.
The absorption of UV-B is crucial because this type of radiation has sufficient energy to cause significant harm to living organisms, including damage to DNA, increased risk of skin cancer, cataracts, and harm to plant life and marine ecosystems.
Importance of the Ozone Layer
The ozone layer's ability to filter UV-B radiation is vital for life on Earth. By absorbing UV-B in the stratosphere, the ozone layer prevents harmful levels of this radiation from reaching Earth's surface. Without this protective layer, UV-B levels would be much higher, posing a severe threat to human health and ecosystems worldwide. The ongoing cycle of ozone breaking down and reforming effectively dissipates the energy from UV-B photons as heat in the stratosphere.
