Tag: global environmental change

When oxygen molecules absorb ultraviolet photons and undergo photolysis, ozone is obtained
$3O _2 \xrightarrow [photolysis]{UV : light} 2O _3$.

Ozone shields the surface of the earth from ultraviolet (UV) radiation from the sun. Ozone layer reduces the chances of skin cancer.

40 to 50% depletion in ozone layer occurs in the South polar region.
Ozone is destroyed by collisions with other atoms and molecules.
The large scale destruction of the stratospheric ozone first came into focus in 1987 through the experiments in antarctica.

Depletion of ozone layer is mainly due to Chloroflorocarbons.
Note:
The following describes the destruction of the ozone by chlorofluorocarbons.
Chlorofluorocarbons contains the chlorine molecule which reacts with ozone (O$ _3$) molecule and splits into O$ _2$ and O molecules.
Chlorofluorocarbons are used in refrigerators, air conditioners and aerosol sprays. They damage the ozone layer of the atmosphere.

Destruction of ozone can cause skin cancer, cataract and can hinder growth of plant. Ozone prevents the harmful radiations from reaching the surface of earth. The UV radiation has enough energy to cause adverse effects on all life systems, especially humans. It can destroy parts of DNA molecules that stores and propagate genetic information from one generation to another generation.

A chlorofluorocarbon (CFC) is composed of carbon, chlorine, and fluorine. This is used in refrigerants, propellants, and solvents. The chlorine atoms are released due to splitting of CFC by ultravoilet radiation.

The presence of CFCs in the atmosphere results in the depletion of the ozone layer. The chemical formula of this substance is CF$ _2$Cl$ _2$. They are used as coolants in refrigerators, coolers, etc. The CFCs causes the breaking of the ozone molecule which forms the oxygen radical and O$ _2$. The depletion of the ozone layer results in the penetration of the harmful UV radiations from the sun into the Earth's atmosphere. 

The correct answer is Stratosphere. Option C

Chlorofluorocarbons or Chlorofluoromethane are also known as freon or aerosols. They are chemicals used as refrigerants, propellants and solid plastic foams. These chemicals are also released as aerosols by jets flying at high altitudes. Along with nitrogen oxides, chlorofluorocarbons react with ozone of ozonosphere and depletes the same. Chlorofluorocarbons release reactive chloride which directly reacts with ozone molecules setting a chain reaction.