AIR

• Air is a mixture of gases.It contains mainly nitrogen and oxygen.
• The Troposphere is the atmospheric layer closest to the surface of the earth.It contains the largest percentage of the total mass of the atmosphere.
• The stratosphere is the second major layer of air in the atmosphere.Ozone is formed in stratosphere.
• This layer of calm and clear air is preferred for high speed jet flights because of the absence of air pockets.
• Above stratosphere is Mesosphere, it extends from 50 to 80 km.
• Above mesosphere lies the Ionosphere, which has electrically conducting layers that help in radio communication.
• The Thermosphere is located above the mesosphere .
• The atmospheric pressure is measured by an instrument called a Barometer.
• SI unit of pressure is Pascal. since pascal is a very small unit of pressure, we normally express pressure in kilopascal (kPa)