Layers of the Earth’s atmosphere—identify the incorrect statement Which of the following statements about the troposphere, stratosphere, and mesosphere is WRONG for atmospheric science and environmental engineering practice?

Introduction / Context:
Understanding the structure of the atmosphere is fundamental in environmental engineering, air-pollution control, and radio communication. Each layer—troposphere, stratosphere, mesosphere, thermosphere/ionosphere—has distinct properties that influence weather, ozone chemistry, and the propagation of electromagnetic waves.

Given Data / Assumptions:

• Troposphere is the lowest layer, where most weather and clouds occur.
• Stratosphere lies above the troposphere and contains the ozone layer.
• Mesosphere lies above the stratosphere with low pressure and temperature.
• Long-distance high-frequency radio communication commonly relies on reflection/refraction by the ionosphere.

Concept / Approach:
The correct identification hinges on which layer reflects radio waves used in long-distance communication. It is not the stratosphere but the ionosphere (part of the thermosphere) that affects radio propagation. The other listed statements about troposphere dust/clouds and stratospheric ozone are standard facts in atmospheric science.

Step-by-Step Solution:

Verification / Alternative check:
Radio engineering and atmospheric references consistently describe the ionosphere (approximately 60–1000 km altitude) as the region responsible for reflecting/refracting HF radio waves, enabling beyond-line-of-sight communication.

Why Other Options Are Wrong:

• Option A: Correct—stratosphere with ozone layer shields UV radiation.
• Option B: Correct—mesosphere exhibits very low pressure and temperatures.
• Option C: Correct—troposphere contains most aerosols, clouds, and weather.

Common Pitfalls:
Confusing stratosphere with ionosphere because both are above the troposphere. Only the ionosphere significantly affects HF radio propagation.

Final Answer:
Long-distance radio waves are reflected back to Earth by the stratosphere.