Question

For the ‘greenhouse effect’ consider statements I to III.

(I) Sunlight is received by Earth. Some incoming radiations are reflected back into space by the atmosphere and some is absorbed such as certain $UV$ light by stratosphere ozone
(II) Earth’s surface emits $IR$ radiations.
(III) Emitted $IR$ radiations are less intense than that emitted by Earth’s surface. $C{O}_2$ along with $IR$ radiations warm the atmosphere.
Select the correct statements.

• A. Both I and II
• B. Both I and III
• C. I, II and III
• D. Both II and III

Answer 1

Answer: (C)

$C{O}_2\left(g\right)$ is not assumed to be an air pollutant because it is non-toxic. However, a buildup of $C{O}_2\left(g\right)$ in the atmosphere may disturb energy balance on earth. Its atmosphere is transparent to visible and $UV$ radiation form the Sun. Infrared radiation is absorbed at earth’s surface and warms it. But some of this absorbed energy is reradiated as $IR$ radiation. Certain atmospheric gases as $C{O}_2$ and water vapour absorb these IR radiations. Energy retained in the atmosphere produces a warming effect. Thus, thermal energy is retained in a greenhouse-greenhouse effect