CBSE Class 10 Science 2023 · Paper 31/4/2 · Question 21

(i) At the higher levels of the atmosphere, ozone (${\text{O}}_3$) shields the surface of the earth from the ultraviolet (UV) radiation of the Sun by absorbing much of it. This radiation is highly damaging to organisms; in human beings it is known to cause skin cancer. (ii) The sharp drop in the 1980s has been linked to synthetic chemicals called chlorofluorocarbons (CFCs), used as refrigerants and in fire extinguishers. Released CFCs reach the ozone layer, where UV radiation breaks them down and sets free chlorine atoms, which break ozone molecules down; each chlorine atom can destroy many ozone molecules.