Question

Ozone is good

• A. in the troposphere
• B. in the mesosphere
• C. in the stratosphere
• D. in the thermosphere

Hint:

• Stratospheric Ozone ("Good Ozone"): Forms the ozone layer, absorbs harmful UV radiation from the sun, protecting life on Earth. Located in the stratosphere.
• Tropospheric Ozone ("Bad Ozone"): A major air pollutant at ground level, component of smog, harmful to health and vegetation. Located in the troposphere.
• The question "Ozone is good" refers to its beneficial role in the stratosphere.

Answer 1

The Correct Option is C

Ozone (O$_3$) plays a dual role in the atmosphere, depending on its location:

• Stratospheric Ozone (Good Ozone): The vast majority of atmospheric ozone (about 90%) is found in the stratosphere, forming the "ozone layer." This layer is beneficial because it absorbs most of the Sun's harmful ultraviolet (UV-B and UV-C) radiation. This absorption protects living organisms on Earth from the damaging effects of excessive UV exposure, such as skin cancer, cataracts, and harm to ecosystems. Therefore, ozone in the stratosphere is considered "good."
• Tropospheric Ozone (Bad Ozone): Ozone is also found in the troposphere (the lowest layer of the atmosphere where we live). Here, it is considered an air pollutant and a primary component of photochemical smog. Ground-level ozone is harmful to human health (causing respiratory problems), damages plants, and contributes to the greenhouse effect. Therefore, ozone in the troposphere (option a) is considered "bad."

The mesosphere (option b) and thermosphere (option d) are layers above the stratosphere. While some ozone may be present, the significant protective "ozone layer" is specifically located in the stratosphere. Therefore, ozone is considered "good" primarily for its role in the stratosphere. \[ \boxed{\text{in the stratosphere}} \]