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Originally Posted by AlexN
Fair enough.. Gotta start somewhere I suppose..
As far as radio waves are concerned, yes, within the vacuum of space they travel at the speed of light, then they enter Earths atmosphere and slow up...
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Just to be clear, the speed of light (radio in this case) in a given medium, is proportional to the speed of light in a vacuum (299792458m/s), and inversly proportional to the Refractive Index of that medium.
When an electromagnetic wave transitions between different medium boudaries, it's velocity (speed & direction) must change. We still call this speed 'c' as it is the fastest speed posiable in that medium, even though it is now less then 299792458m/s.
Also, a simple way to determine the amount of directional change is to apply Snell's Law:
n SIN(i) = n' SIN(r)
Where n & n' are the respective Refractive Indices, and i & r are the deviation from perpendicular of the Incident ray & the Refracted ray.
I say simple because the more exact way to measure refraction is very complex and involves calculating the values of the wave phase and transition mediums at quantum levels and treating all points as harmonic oscillaters
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