Question
What causes tropospheric ducting?
Answer Options
- A) Discharges of lightning during electrical storms
- B) Sunspots and solar flares
- C) Updrafts from hurricanes and tornadoes
- D) Temperature inversions in the atmosphere
Correct Answer: D
Explanation
Tropospheric ducting (T3C06) is caused by specific weather patterns, particularly temperature inversions in the atmosphere. Normally, air temperature decreases with altitude. A temperature inversion occurs when a layer of warmer air sits on top of a layer of cooler air near the Earth’s surface.
This difference in temperature creates a sharp change in the refractive index of the air, which can trap VHF and UHF radio waves. This trapping effect, called a ‘duct,’ guides the signal over the horizon for long-distance contacts.
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