ICSE-IX-Geography
12: Composition and Structure of the Atmosphere
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- #Section : II. Short Answer Questions
- Qstn #1What is known as atmosphere ?Ans : The blanket of air upto 1500 km surrounding the earth is known as atmosphere.
- Qstn #2State the gaseous composition of the atmosphere.Ans : The atmosphere consists of 78% Nitrogen 21% oxygen and 1% other gases.
- Qstn #3Mention any three functions of the atmosphere.Ans :
- Air has weight and exerts pressure. Being pressed down it always remains in contact with land and water.
- Due to their physical contact, exchange of gases between air, land and water takes place on a continuous basis.
- Soil absorbs oxygen and nitrogen due to this contact. Water vapours in air rise from oceans on account of evaporation.
- Qstn #4Name the four layers of the atmosphere.Ans : Four layers of the atmosphere are :
- Troposphere
- Stratosphere
- Mesosphere
- Thermosphere
- Qstn #5What is known as troposphere ?Ans : Troposphere is the lowest and densest layer of atmosphere touching the land surface. It extends from 8km to 18 km. in height
- Qstn #6Mention the chief characteristics of stratosphere.Ans : There is total absence of water vapour in this layer. It extends upto a height of 50 km. The temperature remains constant up to - 55°C.
- Qstn #7In which layer of atmosphere do all weather conditions occur ?Ans : Troposphere is the layer where all weather conditions occur in different forms.
- Qstn #8Name the constituent gases of atmosphere which scientists consider responsible for climate change.Ans : Carbon dioxide and ozone are responsible for climate change, as carbon dioxide absorbs heat from sun and by radiation from the earth; ozone absorbs extremely hot ultra-violet rays controlling the ideal temperature conditions on the earth.
- Qstn #9What is known as ozone layer ?Ans : Stratosphere contains sufficient amount of ozone which absorbs the extremely hot ultra violet rays of the sun. It is known as ozone layer.
- Qstn #10What is leading to depletion of ozone layer in the atmosphere ?Ans : Excessive emission of carbon monoxide and CFCs from industries and vehicles take out the oxygen from ozone layer to form different compounds (oxides). In this way the depletion of ozone layer takes place.
- Qstn #11What is known as Global Warming?Ans : Global Warming is the increase in temperature of earth due to enhanced concentration of Greenhouse gases (CFCs) in the atmosphere.
- Qstn #12Name important Greenhouse gases.Ans : The main Greenhouse gases are CFCs (Chlorofluorocarbons) and nitrogen oxides which are emitted by fertilizers industries and transport engines along with carbon dioxide and methane.
- Qstn #13Name two chief characteristics of atmosphere.Ans : Atmosphere protects earth from harmful ultra-violet and infra-red rays of the sun. It controls the hydrological cycle and provide life giving gases.