What does the ozone layer do?

• A. Traps heat in atmosphere
• B. A region of the stratosphere with high concentration of ozone protecting from UV
• C. Source of oxygen
• D. Causes acid rain

Answer: (B)

The main idea here is that the ozone layer acts as a UV shield. It sits in the stratosphere with a relatively high concentration of ozone (O3), and this ozone absorbs most of the Sun’s ultraviolet radiation, especially the more harmful UV-B and UV-C rays. By filtering out these rays, it helps protect living organisms from DNA damage, skin cancer, and cataracts, as well as protecting ecosystems.

It’s not primarily about trapping heat—the greenhouse effect does that with other gases. It’s not the main source of atmospheric oxygen, since oxygen comes largely from photosynthesis, and ozone is just a small molecule formed in the upper atmosphere. And it doesn’t cause acid rain; acid rain results from pollutants like sulfur dioxide and nitrogen oxides reacting in the atmosphere, not from ozone.