Assertion (A) : Presently, the global atmosphere is warming up.
Reason (R): The depletion of stratospheric ozone layer has resulted in increase in ultraviolet radiations reaching the Earth.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark a
B. lf both Assertion & Reason are true but the reason is no t the correct explanation of the assertion, then mark b
C. If Assertion is true statement but Reason is false, then mark c
D. If both Assertion and Reason are false statements, then mark d.

Answer

B

Explanation

The warming up of global atmosphere present day is due to the increase in green house effect. Green house effect (GHE) describe the roles of water vapour, `CO_(2)` and other trace gases in keeping the Earth's surface warmer than it would be otherwise. These radiatively active gases are relatively transparent to incoming shortwave radiation (visible spectrum), but are relatively opaque to outgoing reradiating (infared rays) longwave radiation. The latter radiation, which would otherwise escape to space, is trapped by these gases within the lower levels of the atmosphere. The subsequent reradiation of some of the energy back to the surface maintains surface temperature higher than they would be if the gases were absent (without the green house effect the Earth's average golobal temperature would be-18 degree celsius rather than the present 15 degree celsius). There is concern that increasing concentration of the green house gases including `CO_(2), CH_(4)` and man made chlorofluorocarbons (CFCS), may enhance the green house effect and cause global warming.

Ozone layer present in the stratosphere is depleted by the aerosols and chloroflurocarbons. Ozone protects the earth from high energy ultra violet radiation.