Tag: ozone and its depletion

The ozone layer is important because it absorbs ultraviolet (UV) radiation from the sun, preventing most of it from reaching the earth's surface. Radiation in the UV spectrum has wavelengths just shorter than those of visible light.

The ozone layer acts as a filter for the shorter wavelength and highly hazardous ultraviolet radiation (UVR) from the sun, protecting life on Earth from its potentially harmful effects. When the sky is clear, there is an inverse relationship between stratospheric ozone and solar UVR measured at the Earth’s surface. That is,the lower the ozone levels, the higher the solar UVR.

Ozone in stratosphere is depleted by chlorofluorocarbon, such as $CF _2Cl _2$.
It is dichlorodifluoromethane also known as freon-12.

Air pollution is formed through the reaction of solar radiation with airborne pollutants like nitrogen oxides and volatile organic compounds. These compounds, which are called primary pollutants, are often introduced into the atmosphere through automobile emissions and industrial processes. Ultraviolet light can split nitrogen dioxide into nitric oxide and monatomic oxygen; this monatomic oxygen can then react with oxygen gas to form ozone. 

Ozone $\displaystyle O _3$ gas is known to shield the earth from harmful ultraviolet radiation. 

In the stratosphere, ozone $\displaystyle O _3 $ screen out a large fraction of the ultraviolet rays of the sun. Thus, ozone acts as a protective shield. Thus, due to presence of ozone layer, the harmful ultraviolet rays cannot penetrate earth's atmosphere. Hence, they cannot reach us.

The ozone depletion was related to halogen (chlorine)-catalyzed chemical reaction which takes place in the spring season in the Antarctic polar region. The chlorine is derived from manmade chlorofluorocarbons and reacts with nitric acid forms chlorine nitrate($ClONO _2$) (CFCs) in the stratosphere.

Hence option D is correct. 

The two forms of oxygen found in the atmosphere are a diatomic molecular form that has chemical formula as O$ _2$ or oxygen, the life-giving gas that we breathe in to survive. 
Another  is a triatomic molecular form that has chemical formula as O$ _3$ called ozone gas, it protects us from harmful UV rays.
In water, oxygen is found as a compound with hydrogen molecules. The oxygen in water is dissolved oxygen used by aquatic animals and plants.
carbon dioxide has 2 molecules of oxygen with one molecule of carbon. It is formed by the reaction between carbon molecules and oxygen molecules during fermentation or respiration.
In the case of water and carbon dioxide, the oxygen does not exist independently but in association with other molecules. Whereas in the case of ozone and oxygen, the oxygen exists independently. Hence, the two forms of oxygen are ozone and oxygen.
The correct option is C (Ozone and Oxygen).

The ozone layer or ozone shield refers to a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet (UV) radiation. It contains high concentrations of ozone ($O _3$) relative to other parts of the atmosphere, although still very small relative to other gases in the stratosphere.