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?
- A They pass through the ionosphere
- B They are bent back to the Earth
- C They are changed to a frequency above the MUF
- D They 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
How signals travel: the ionosphere and its layers, skip, ground wave, sporadic E, and which bands work when.