Question

Assertion : Contribution of $C{O}_2$, $C{H}_4$, $CFCs$ and $N_{2}O$ towards greenhouse effect is respectively $60\%$, $6\%$, $14\%$ and $20\%$.
Reason : Greenhouse gases are radioactively active gases which prevent the short wavelength radiations emitted by earth to escape into space.

• A. If both assertion and reason are true and reason is the correct explanation of assertion
• B. If both assertion and reason are true but reason is not the correct explanation of assertion
• C. If assertion is true but reason is false
• D. If both assertion and reason are false

Answer 1

Answer: (D)

The gases which are transparent to solar radiation but retain and partially reflect back long wave heat radiations are called greenhouse gases $(GHGs)$. Greenhouse gases are essential for keeping the earth warm and hospitable. The various greenhouse gases are $C{O}_2$ (warming effect $60\%$), $C{H}_4$ (effect $20\%$), chlorofluorocarbons or $CFCs$ $(14\%)$ and nitrous oxide $(N_{2}O$, $6\%)$. Others of minor significance are water vapours and ozone.