Which statement best describes stratospheric ozone?

Which statement best describes stratospheric ozone?

• A. It enhances photochemical smog in the troposphere
• B. It is not important to atmospheric health
• C. It blocks UV-B radiation in the stratosphere
• D. It is formed only by volcanic activity

Answer: (C)

Stratospheric ozone acts as a shield by absorbing ultraviolet radiation, especially UV-B, in the stratosphere. This ozone is formed when UV light splits oxygen molecules (O2) into individual atoms, which then join with O2 to make ozone (O3). The ozone molecules absorb UV-B photons, preventing much of this harmful radiation from reaching Earth's surface, which helps protect living organisms and ecosystems. This shielding effect is the best description because it directly addresses what stratospheric ozone does and why it matters for atmospheric health. The other statements don’t fit because photochemical smog is driven by ozone formed in the lower atmosphere (troposphere) from human-emitted precursors, not by stratospheric ozone, so stratospheric ozone does not enhance smog. Ozone in the atmosphere is indeed important for health, so saying it’s not important is incorrect. Finally, ozone is formed primarily through photochemical reactions driven by solar radiation, not by volcanic activity, so it isn’t formed only by volcanic activity.

Stratospheric ozone acts as a shield by absorbing ultraviolet radiation, especially UV-B, in the stratosphere. This ozone is formed when UV light splits oxygen molecules (O2) into individual atoms, which then join with O2 to make ozone (O3). The ozone molecules absorb UV-B photons, preventing much of this harmful radiation from reaching Earth's surface, which helps protect living organisms and ecosystems. This shielding effect is the best description because it directly addresses what stratospheric ozone does and why it matters for atmospheric health.

The other statements don’t fit because photochemical smog is driven by ozone formed in the lower atmosphere (troposphere) from human-emitted precursors, not by stratospheric ozone, so stratospheric ozone does not enhance smog. Ozone in the atmosphere is indeed important for health, so saying it’s not important is incorrect. Finally, ozone is formed primarily through photochemical reactions driven by solar radiation, not by volcanic activity, so it isn’t formed only by volcanic activity.