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प्रश्न
Why does all the water of the earth not get evaporated during hot summer days ?
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उत्तर
Evaporation is a surface phenomenon and can cause vaporization only at the surface. Not all the water on earth is exposed to sun's heat as most of this water remains below the surface of various water bodies. Besides, some water on earth is in the form of ground water laying below the ground surface, where the atmospheric heat cannot cause much effect.
Moreover, not all the parts of Earth receive summers at the same time. Rate of evaporation will be slow or evaporation might be altogether absent at places where summers are yet to start. Similarly, evaporation is also effected by humidity and wind patterns which are local phenomena. Therefore, a place at a particular time might receive a rainfall while at the same time an adjacent geographic region has a high temperature and bright sun. Thus, all the water on Earth's surface cannot evaporate altogether.
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संबंधित प्रश्न
What is evaporation?
Water in a dish evaporates faster than in a bottle. Give reason.
Why is cooling produced on evaporation of a liquid?
Why is heat energy needed to melt a solid ? What is this heat energy called ?
If the back of your hand is moistened with alcohol, you will find that it rapidly becomes dry. Why is it that while it is drying, your hand feels cool ?
Why does our palm feel cold when we put some acetone (or perfume) on it ?
Why does evaporation cool a liquid ?
How is humidity measured?
Give a geographical reason:
Air becomes saturated.
Look at Fig. 1.3 and suggest in which of the vessels A,B, C or D the rate of evaporation will be the highest? Explain.

