Which region of the atmosphere can reflect HF radio waves?
The stratosphere
The troposphere
The ionosphere✓الإجابة الصحيحة
The electrosphere
الشرح
The ionosphere is the region ionised by solar radiation, roughly 60 to 400 km up, and its free electrons bend HF signals back toward the ground. The troposphere and stratosphere are not ionised, so they cannot return HF waves in this way.