Which of the following gas is found in the Stratosphere?

The correct answer is Option (1) → Ozone

Option (1) Ozone — Correct. The ‘good’ ozone of the stratosphere is the ozone layer. It absorbs the harmful UV rays of the sun. CFCs released by humans are thinning it, as in the ozone hole over Antarctica.

Option (2) Carbon dioxide — Incorrect. Carbon dioxide is the main greenhouse gas. Its effect is felt in the lower atmosphere, where it traps heat and causes global warming.

Option (3) Methane — Incorrect. Methane is another greenhouse gas of the lower atmosphere. It is not the gas that forms the protective layer of the stratosphere.

Option (4) Hydrogen — Incorrect. Hydrogen gas is not a part of the ozone layer and plays no role in shielding the earth from UV rays.

Note: This question is from Chapter 16, Environmental Issues, of the pre-rationalised NCERT book. This chapter is not in the present NCERT book (2026-27). The extract below is from the pre-rationalised edition.

NCERT Extract (Pre-rationalised edition, Chapter 16, Environmental Issues):
Ozone Depletion in the Strato- – “… You have earlier studied in the Chemistry textbook of Class XI about ‘bad’ ozone, formed in the lower atmosphere (troposphere) that harms plants and animals. There is ‘good’ ozone also; this ozone is found in the upper part of the atmosphere called the stratosphere, and it acts as a shield absorbing ultraviolet radiation from the sun.”