Basic Qualification · B-007 Radio wave propagation · B-007-002-004
Which region of the ionosphere is the least useful for long-distance radio-wave propagation?
- A The F2 region
- B The F1 region
- C The E region
- D The D region
Correct answer: D — The D region. From the official ISED question bank, verified word for word.
Why
The D region sits lowest in the ionosphere and acts like a sponge that absorbs radio signals rather than bouncing them back to Earth, making it useless for long-distance communication. 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.