Basic Qualification · B-007 Radio wave propagation · B-007-002-007
When is ionization at a minimum in the ionosphere?
- A Shortly before midnight
- B Shortly before dawn
- C Just after noon
- D Just after dusk
Correct answer: B — Shortly before dawn. From the official ISED question bank, verified word for word.
Why
The ionosphere needs sunlight to keep its atoms ionized, so as night stretches on without the sun, the ionization slowly fades away. 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.