CBSE Class 10 Science 2023 · Paper 31/2/3 · Question 26

Ozone (${\text{O}}_3$) is a molecule of three oxygen atoms. Unlike oxygen (${\text{O}}_2$), which aerobic life needs, ozone is a deadly poison if it is breathed in, and near the ground it is a harmful pollutant. But at the higher levels of the atmosphere ozone forms a layer that absorbs most of the ultraviolet (UV) radiation from the Sun and so shields the surface of the earth from it. UV radiation is highly damaging to organisms — in human beings it is known to cause skin cancer — so this ozone protects the earth and its inhabitants. That is its essential function. It is formed there by the action of UV on oxygen: ${\text{O}}_2\stackrel{\text{UV}}{\to }\text{O}+\text{O}$, then $\text{O}+{\text{O}}_2\to {\text{O}}_3$.