Basic Qualification · B-007 Radio wave propagation · B-007-006-006
What usually happens to radio waves with frequencies below the maximum usable frequency (MUF) when they are sent into the ionosphere?
- AThey pass through the ionosphere
- BThey are bent back to the Earth
- CThey are changed to a frequency above the MUF
- DThey are completely absorbed by the ionosphere
Correct answer: B — They are bent back to the Earth. From the official ISED question bank, verified word for word.
Why
When radio waves below the maximum usable frequency enter the ionosphere, the charged particles there act like a mirror, bending the signal back down toward the ground instead of letting it escape into space. The full explanation — and one for every question — is in Pro.
Practise this section
Radio wave propagation is section B-007 of the Basic exam: How signals travel: the ionosphere and its layers, skip, ground wave, sporadic E, and which bands work when.
Drill B-007 — free, no account