- No. i. What do you mean by atmosphere?
Answer. Atmosphere is the envelope of different gases around-the Earth. It extends continuously from the Earth’s surface outwards without any boundary. About 99% of atmospheric mass lies within 30 kilometers of the surface and 75% lies within the lowest 11 kilometers.
- No. ii. What is difference between atmosphere and environment?
Answer. Environment refers to biosphere and hydrosphere whereas atmosphere refers to air and its components. Atmosphere is related to weather and environment is concerned with climate.
- No.iii. Name the major constituents of troposphere.
Answer. Troposphere is the lowest region of the atmosphere. It extends up to 12km upwards from the Earth’s surface. It consists of different gases. The major gases present in troposphere are nitrogen (78%) and oxygen (21%). These two gases comprise 99% by valance of the Earth’s atmosphere.
- No.iv. How the temperature of atmosphere is maintained?
Answer. Solar radiations reach up to the Earth and are absorbed by it. Then, this solar energy is (visible light) radiated as heat energy (infrared radiations) by the Earth. Keep in mind, wave length of visible light is shorter than that of infrared radiations radiated by the Earth. Due to this, visible light can pass through a medium from which infrared radiations cannot pass.
Carbon dioxide and water vapours present in the atmosphere are good infrared radiations absorber. Both of these gases allow the visible light to pass through it that reaches up to the Earth. But when Earth radiates the heat the form of infrared radiations, these gases absorb much of the outgoing infrared radiation that keeps the atmosphere warm. Thus presence of carbon dioxide and water vapours is responsible for maintaining the temperature of the atmosphere.
- No. v. Where the ozone layer exists?
Answer. Ozone gas is found in stratosphere. Stratosphere region lies above the troposphere region and covers from 12 to 50 km of the atmosphere. It is considered that in the middle of the stratosphere formation of ozone takes place by the combination of oxygen molecule and atomic oxygen such as.
O2 + O ————> O3
Hence, formation of ozone in this region results in formation of ozone layer. Thus ozone layer exists about 25km to 30km away from the Earth’s surface.