- No.vi. Why the temperature of upper stratosphere is higher?
Answer. Stratosphere is further divided into three layers upper, middle and lower region. The presence of ozone in stratosphere region is responsible for the rise of temperature due to absorption of radiations. Within this region, temperature increases as altitude increases, such as lower layer temperature is about -58°C and upper layer is about 2°C. It is because ozone’s upper layer absorbs high energy ultraviolet radiation coming from the son while lower layer receives very low UV- radiations.
Test Yourself 14.2 (POLLUTANTS)
- No. i. What do you mean by an air pollutant?
Answer. The harmful substances present in air are called air pollutants. Even a beneficial substance beyond a specific concentration may be harmful. Air pollutants change the weather, badly affects the human health, damage the plants and destroy buildings.
- No. ii. Name three primary air pollutants.
Answer. Primary pollutants are the waste or exhaust products driven out because of combustion of fossil fuels and organic matter. These are oxides of sulphur (SO2 and SO3); oxides of carbon (CO2 and CO); oxides of nitrogen (especially nitric oxide NO) hydrocarbon (CH4); ammonia and compounds of fluorine.
- No. iii. Identify as primary or, secondary air pollutant, SO2, CH4, HNO3, NH3, H2SO4 O3.
Answer. Primary air pollutant are; SO2, CH4, HNO3
Secondary air pollutant is: NH3, H2SO4 O3.
- No.iv. Why COs is called a greenhouse gas?
Answer. The CO2 in the atmosphere acts like a glass wall of the greenhouse. It has the capability of absorbing some of the infrared radiations emitted by the Earth. Hence, increased concentration of CO2 layer absorbs the infrared radiations emitted by the Earth’s surface and prevents heat energy escaping from the atmosphere. As a result, less heat energy is lost from the atmosphere. Therefore, the average temperature of the atmosphere gradually increases. So CO2 is responsible for increasing the atmospheric temperature. This is called the greenhouse effect. Therefore, CO2 is called as greenhouse gas.
- No. v. Why the flood risks are increasing?
Answer. Accumulation of carbon dioxide in air is resulting in increasing atmospheric temperature about 0.05 °C every year. It is causing major changes in atmospheric circulation resulting in changing weather patterns. It melts glaciers and snow caps that are increasing flood risks and intense tropical cyclones.