Evaporation is one of the basic and important processes in the function of the hydraulic cycle. In this process due to solar radiation, during the day time the water in the liquid form is transformed into gaseous form is called moisture water vapour or humidity. The evaporation occurs on the surface of free water bodies such as oceans, seas, lakes and rivers.
The water in the sub soil also gets evaporated and makes the soil dry. It also occurs from plants and vegetation cover. It also appears in the area covered by sheets of ice, in the polar areas.
The water is made up of a number of molecules and therefore each one of the molecules moves in a different direction with different velocities.
The velocity of the molecule depends upon the temperature. These molecules gets attract towards each other; therefore the force of attraction is proportional to the mass and inversely proportional to the distance squared.
Therefore if the mass is greater the point of attraction will be more and as the distance between two molecules goes on increasing the point of attraction goes on reducing.
The molecules below gets attracted towards the top molecules.
The molecule having more kinetic energy than the attraction in the downward direction escapes into the atmosphere.
The evaporation in the net rate of movement of molecules to and therefore from the water surface.
Factors affecting on Evaporation
- Solar radiation
- Air pressure and altitude
- Quality of water
- Depth of water
- Depth of water
Firstly the temperature of the surface of water and that of the thin layer of air near the water surface is a key factor.
2. Solar radiation
One has calculated that that about 590 calories are required for covering one gram of water into water vapour. Solar radiation receives this energy.
The rate of evaporation depends upon the proportion of evaporated water molecules. If the air near the water surface is removed which already has a high proportion of water molecules through the horizontal movement of air called wind.
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