What is the primary function of the ozone layer?

• A. Trap heat in the atmosphere
• B. Absorb ultraviolet radiation
• C. Provide breathable oxygen
• D. Block all sunlight

Answer: (B)

The main function of the ozone layer is absorbing ultraviolet radiation from the sun. Ozone molecules in the stratosphere (O3) take in high-energy UV photons, especially UV-B and UV-C, which are the wavelengths that can cause skin cancer, cataracts, and genetic damage. By blocking most of this UV light from reaching the surface, the ozone layer protects living organisms and helps maintain stable surface conditions. The energy absorbed becomes heat, which warms the stratosphere a bit, but this is not the same as the greenhouse effect that traps heat in the lower atmosphere. The ozone layer does not provide breathable oxygen—oxygen is produced mainly by photosynthesis and persists as O2 in the air, while ozone itself can be harmful to breathe in at ground level. It also does not block all sunlight; visible light still reaches the surface, so daylight remains.