Discuss brieflythe following:

(a) Greenhouse gases

(b) Catalytic converter

(c) Ultraviolet B

(a) Greenhouse gases: - Thegreenhouse effect refers toan overall increase in the average temperature of the Earth due tothe presence of greenhouse gases. Greenhouse gases mainly consist ofcarbon dioxide, methane, and water vapour. When solar radiationsreach the Earth, some of these radiations are absorbed. Theseabsorbed radiations are released back into the atmosphere. Theseradiations are trapped by the greenhouse gases present in theatmosphere.. This helps in keeping our planet warm and thus, helps inhuman survival. However, an increase in the amount of greenhousegases can lead to an excessive increase in the Earth’stemperature, thereby causing global warming.

(b) Catalytic converter: - Catalytic converters aredevices fitted in automobiles to reduce vehicular pollution. Thesedevices contain expensive metals such as platinum, palladium, andrhodium that act as catalysts. As the vehicular discharge passesthrough the catalytic converter, the unburnt hydrocarbons present init get converted into carbon dioxide and water. Carbonmonoxide and nitric oxide released by catalytic converters areconverted into carbon dioxide and nitrogen gas (respectively).

(c) Ultraviolet-B: - Ultraviolet-B is an electromagneticradiation which has a shorter wavelength than visible light. It is aharmful radiation that comes from sunlight and penetrates through theozone hole onto the Earth’s surface. It induces many healthhazards in humans. UV −B damages DNA andactivates the process of skin ageing. It also causes skin darkeningand skin cancer. High levels of UV −B cause corneal cataract inhuman beings.