How long (in seconds) does it take for a radio wave of frequency 8.94 × 106 s–1 to reach Mars when Mars is 8.2 × 107 km from Earth?
You radio wave should travel at the speed of light in vacuum
so basically it would take (velocity=distance/time rearranged):
Any radio wave is moving at the speed of light, regardless of the frequency, so the frequency should be superfluous information.
The speed is light is close to
I take the distance you are given, to be
Before we actually compute this, we can notice that this is a little more than half the distance of the earth from the sun (150 mill. km), a distance the light uses 500 sek. = 8 min 20 sec. to travel, so we should get about
As the distance is given with 2 significant figures, we round this off to 270 sek = 4 min 30 sec.