Chemistry
The ozone molecules formed by the below reaction absorb ultraviolet radiation having wavelengths between 240 and 310 nm. The triatomic ozone molecule becomes diatomic molecular oxygen plus a free oxygen atom:
O3 + (240 nm < radiation < 310 nm) → O2 + O
The atomic oxygen produced immediately reacts with other oxygen molecules to reform ozone:
O2 + O + M → O3 + M
where "M" denotes the third body that carries off the excess energy of the reaction. In this way, the chemical energy released when O and O2 combine is converted into kinetic energy of molecular motion. The overall effect is to convert penetrating UV light into heat, without any net loss of ozone. This cycle keeps the ozone layer in a stable balance while protecting the lower atmosphere from UV radiation, which is harmful to most living beings. It is also one of two major sources of heat in the stratosphere (the other being the kinetic energy released when O2 is photolyzed into O atoms).
Read more about this topic: Ozone-oxygen Cycle
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