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Question

Discuss briefly the following

(a) Greenhouse gases

(b)  Catalytic converter

(c) Ultraviolet - B


Solution

(a) Greenhouse gases CO2,NO4,CH3,O3,CFCs and water vapour are collectively known as greenhouse gases. They act like a glass sheet used in a greenhouse, to keep the plants warm in winters.

Greenhouse gases, help keep the temperature of Earth at an average of 15C by radiating heat towards the Earth. In the absence of these gases, the Earth's temperature would be much below zero.

(b) Catalytic converters   are fitled into the authomobile exhaust, They have expensive metals (Platinum-palladium and rhodium) as the catalysts.

(i) Unburnt hydrocarbons into carbon dioxide and water.

(ii) Carbon monoxide and nitric oxide to carbon dioxide and nitrogen gas.

Motor vehicles equipped with catalytic converters are much less polluting than the other vehicles.

(c)  Ultravlolet - B   is a part of ultraviolet rediation having a wavelength of 280-320 nm.

It damages DNA by causign mutations that can also result in 

(i) Premature ageing of skin.

(ii) Damage to skin cells and various types of skin cancers.

(iii) Inflammation of cornea, called snow-blindness, cataract, etc.

Ozone layer absorbs 50% of ultraviolet - B and protects us from its harmful effects. But, with recent thinning of ozone layer, these effects are becoming more pronounced.


Biology
NCERT Textbook
Standard XII

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