Sphere of the Earth — Social Science STD 6 — Question
Gujarat BoardEnglish MediumSTD 6Social ScienceSphere of the Earth3 Marks
Question
Short note : Atmosphere
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Answer
The earth is surrounded by a sphere of various gases up to the approximate height of $850$ to $1000 \ km$. This is known as 'Atmosphere'. The atmosphere is transparent, colourless, odourless and tasteless. It contains gaseous, liquid and solid elements (matter).The atmosphere includes nitrogen, oxygen, argon, ozone, carbon dioxide and water vapour. Besides these gases, there are dust particles, saline contents, microorganisms, meteoritic particles, etc. in the atmosphere. The atmosphere near the earth's surface is dense, but the air becomes thin as one goes up from the surface of the earth.
Carbon dioxide is a heavy gas and so it is found in the lower strata of the atmosphere. Its proportion decreases as one goes up. The existence of carbon dioxide is reduced after an altitude of $20 \ km$, that of oxygen after $110 \ km$ and that of nitrogen after $130 \ km$ in the atmosphere. At a very high altitude, only light gases like hydrogen and helium are found.
The proportion of ozone gas is much less in the atmosphere. Dust particles and saline contents are the main solid matter in the atmosphere. These are found in the lower strata of the atmosphere.
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