Question

Question 11: Discuss briefly the following: (a) Greenhouse gases (b) Catalytic converter (c) Ultraviolet B

Class 12 - Biology - Environmental Issues Page 286

Answer 1

) Greenhouse gases: - Thegreenhouse effect refers to an overall increase in the average temperature of the Earth due to the presence of greenhouse gases. Greenhouse gases mainly consist of carbon dioxide, methane, and water vapour. When solar radiations reach the Earth, some of these radiations are absorbed. These absorbed radiations are released back into the atmosphere. These radiations are trapped by the greenhouse gases present in the atmosphere.. This helps in keeping our planet warm and thus, helps in human survival. However, an increase in the amount of greenhouse gases can lead to an excessive increase in the Earth’s temperature, thereby causing global warming.



(b) Catalytic converter: - Catalytic converters are devices fitted in automobiles to reduce vehicular pollution. These devices contain expensive metals such as platinum, palladium, and rhodium that act as catalysts. As the vehicular discharge passes through the catalytic converter, the unburnt hydrocarbons present in it get converted into carbon dioxide and water. Carbon monoxide and nitric oxide released by catalytic converters are converted into carbon dioxide and nitrogen gas (respectively).

(c) Ultraviolet-B: - Ultraviolet-B is an electromagnetic radiation which has a shorter wavelength than visible light. It is a harmful radiation that comes from sunlight and penetrates through the ozone hole onto the Earth’s surface. It induces many health hazards in humans. UV −B damages DNA and activates the process of skin ageing. It also causes skin darkening and skin cancer. High levels of UV −B cause corneal cataract in human beings.

Answer 2

Answer:

(a) Greenhouse gases

This effect refers to the global increase in the average temperature of the Earth as a result of greenhouse gases. These gases are methane, carbon dioxide and water vapor. When solar rays are incident on Earth, some of these are absorbed which are released back into the atmosphere. The greenhouse gases present in the atmosphere trap these radiations which helps in keeping Earth warm, hence suitable for humans to survive. Therefore, increase in the level of greenhouse gases can lead to an increase in the temperature of Earth overall resulting in Global warming.

(b) Catalytic converter

These are devices fixed in automobiles to lessen the vehicular pollution and contain expensive metals such as palladium, platinum and rhodium that serve as catalysts. When the vehicular discharge passes through the catalytic converter, the unburnt hydrocarbons found in it is converted into water and carbon dioxide. Nitric oxide and carbon monoxide liberated by catalytic converters are converted into nitrogen gas and carbon dioxide respectively.

(c) Ultraviolet-B

It is an electromagnetic radiation possessing a short wavelength compared to the visible light. They are produced by Sun, and are harmful rays which penetrate through the ozone hole on the surface of the Earth. UV-B poses many health hazards in humans, it damages DNA, activating the skin ageing process. These rays are also known to cause skin cancer and skin darkening. High levels of UV-B causes corneal cataract in humans.