Hello! I am having a problem with this problem about the reflection of a "radio wave" in the high atmosphere. (ionosphere) "A short-length wave receiver receive two signals from a distant source at 500Km, beeing those signals, one from the normal conduction through the atmosphere and the second from the reflection of this wave in the ionosphere, that behaves like a mirror for this kind of wave. Consider the ionosphere at 200Km from the ground. We have, the frequency of the source is 10Mhz and the signal transmited varies through two maximuns 8 times per minute. This happens because the displacement of the ionosphere. Which is the velocity of the ionosphere. (assume that the Earth surface is almost plane and that the wave do not suffer any kind of turbulence or other dampings in the air)" I can't figure this question out. The point of the reflection and the way the ionosphere is moving to make this "delay". Can anyone help me with this? Thank you, Aron PS- I don't know exactly if the term "ionosphere" is correct, in my language it is something like that for this part of the atmosphere but the name in fact doesn't matter, either the problem doesn't ask for any previsius knowledge of it.