A space probe produces a radio signal pulse. If the pulse reaches Earth 12.3 seconds after it is emitted by the probe, what is the distance from the probe to Earth?

Distance = 3.69 * 10^9 m

The distance from the probe to Earth is 3.69 * 10^9 m

Explanation:

Distance from the probe to the Earth can be derived using the simple motion formula;

Distance = speed * time ... 1

Since a radio signal uses an electromagnetic wave to transfer signal, it has the same speed as the speed of light.

Speed of radio signal = speed of light = 3.0 * 10^8 m/s

time taken to reach the earth = 12.3 seconds

Substituting the values of speed and time into equation 1;

Distance = 3.0 * 10^8 m/s * 12.3 s

Distance = 36.9 * 10^8 m

Distance = 3.69 * 10^9 m

Note: all electromagnetic radiation have the same speed which is equal to 3.0 * 10^8 m/s