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

Explanation

(a) Greenhouse gases : Gases that trap the heat of the sun in the earth.s atmosphere increasing atmospheric temperature effect are called greenhouse gases. `CO_(2), CH_(4), N_(2)O  and CFC` cause greenhouse. In the absence of greenhouse gases, the temperature of earth would go down to `-18^(@)C`. The net effect of higher GHGs will be disastrous, (i) Melting of polar ice caps and mountain snow caps resulting in rising of sea level threatening submergence of many islands and coastal areas. Odd climate changes like El Nino. Increased floods and drought.
(b) Catalytic converter : Catalytic converter .are used to reduce emission of poisonous gases like nitrogen oxides, carbon monoxide & unreacted hydrocarbon in automotive emission. It is made of platinum, palladium and rhodium and is used as catalyst. It converts unburnt hydrocarbons into `CO_(2)`. The only precaution required is not to use gasoline having lead as lead inactivates the catalysts of the converter.
(c) Ultraviolet B: Ultraviolet B is one of the three types of invisible light rays given off by the sun. Ultraviolet B penetrates the ozone layer in attenuated form and reaches earth. This is more over equator than poles due to thinning of ozone shield over equator. It causes skin cancer, reduce rate of photosynthesis in phytoplankton, reduces diversity of aquatic ecosystem.