It is an inexhaustible natural resource. It is very essential for the survival of all the living organisms on earth. In atmosphere, about 95% of the total air is present up to a height of 20 km above the earth's surface. The remaining 5% of air is present up to a height of about 280 km. Air is a mixture of different gases; nitrogen and oxygen are the major components. Thus, total volume of air present in atmosphere consists of 78% nitrogen 21% oxygen and remaining 1% is made up of other gases such as argon, neon, helium, krypton, xenon and radon.
Sub Topics * Atmosphere * Composition of atmospheric air * Note:
Atmosphere
A thick gaseous envelope surrounding the earth is called atmosphere. The density of air in the atmosphere varies with altitude.
Atmosphere is divided into five different layers or zones: * Troposphere * Stratosphere * Mesosphere * Ionosphere * Exosphere
Composition of atmospheric air
Gas | Relative %age Volume | Nitrogen (N2) | 78.09 | Oxygen (O2) | 20.93 | Argon (A) | 00.93 | Carbon di oxide (CO2) | 0.032 | Miscellaneous | 0.02 | Total | 100.000 |
Oxygen is present in the first zone, 10 to 12 km from the surface of the earth. This zone is called troposphere. Therefore, at higher altitudes, some of us find it difficult to breathe. Above the troposphere is the stratosphere. This zone is rich in ozone. Hence, it is also called ozonosphere.
In ozonosphere, the sunlight converts oxygen to ozone by photochemical dissolution. The ozonosphere completely absorbs short wave solar radiations, such as ultraviolet (uv) radiations, x-rays, gamma rays etc. from the Sun. Oxygen and ozone of stratosphere provide protection from harmful solar radiation. It protects us from the bad effects of ultraviolet rays of sunlight. The effects of ultraviolet radiations are: * Cataract - eye lens becomes opaque causing blindness * Inflammatory diseases * Skin cancer
Scientific studies have indicated