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Question

Why ozone hole forms over Antarctica ? How will enhanced ultraviolet radiation affect us ?


Solution

Ozone hole forms over Antarctica because of increased accumulation. of ozone depleting substances like CH4,N4O, chlorofluorocarbons (CFCs) released from ACs and refrigerators, fire extinguishers and jet fuels.

(i) When released in stratoshere, these substances drift towards the poles and get accumulated on the ice clouds formed at high altitudes.

(ii) Ice provides a surface on which breakdown of all the CFC compounds takes place to release chlorine atom.

(iii) These chlorine atoms breakdown ozone resulting in thinning of the ozone layer.

Normally, the ozone layer plays a protective role by absorbing harmful UV radiations but reduction in its thickness allows UV rays to reach Earth's surface.

Effects of ultraviolet radiation on humans

(i) Early ageing of skin.

(ii) Increased incidences of cancer of the skin.

(iii) Cataract of the eyes.

(iv) Inflammation of cornea of the eye (known as snow blindness).

(v) Weakened immune system.


Biology
NCERT Textbook
Standard XII

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