CBSE Class 10 Science 2019 · Paper 31/1/3/C · Question 10

Ozone (${\text{O}}_3$) is a molecule made of three oxygen atoms. At the higher levels of the atmosphere it forms a layer that shields the Earth from the Sun's ultraviolet (UV) radiation. Formation: high-energy UV radiation splits some oxygen molecules into free oxygen atoms, which then combine with oxygen molecules to form ozone: ${\text{O}}_2\stackrel{\text{UV}}{\to }\text{O}+\text{O}$; $\text{O}+{\text{O}}_2⟶{\text{O}}_3$. If the ozone layer is continuously damaged (mainly by CFCs), more UV radiation will reach the surface of the Earth. Consequences (any two): (i) skin cancer in human beings; (ii) damage to the eyes, such as cataract; (iii) a weakened immune system; (iv) harm to crops and to aquatic life.