Technician exam question T3C11
Subelement T3, RADIO WAVE PROPAGATION· Group T3C
Why is the radio horizon for VHF and UHF signals more distant than the visual horizon?
- A.Radio signals move somewhat faster than the speed of light
- B.Radio waves are not blocked by dust particles
- C.The atmosphere refracts radio waves slightly (correct answer)
- D.Radio waves are blocked by dust particles
WhyThe radio horizon for VHF and UHF signals is more distant than the visual horizon because the atmosphere refracts radio waves slightly. The atmosphere's density gradually decreases with altitude, and that gradient slightly bends (refracts) radio waves downward as they travel, letting VHF and UHF signals curve gently around the Earth's curvature and reach somewhat past where a perfectly straight optical line of sight would end, answer C. Radio waves don't travel faster than light (A), and while dust particles are irrelevant to either radio or visual horizon distance in the way B and D suggest, the actual reason for the radio horizon's extra reach is atmospheric refraction, not anything to do with dust.
Published 2026-08-28 · Last updated 2026-08-28 · Question text is verbatim from the 2026-2030 NCVEC Element 2 pool (public domain); the explanation above is original writing, see our methodology.
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