Answer:
13.5 ms
Explanation:
The sound wave travels with uniform motion in both cases, so the time taken to cover a distance d is given by:
where
d is the distance to cover
v = 340 m/s is the speed of sound in air
So for the people across the newsroom,
d = 4.7 m
So the time taken is
The radio waves instead travels with uniform motion at the speed of light:
So the time taken for them is
where
d = 82 km = 82,000 m
is the distance of the people who are 82 km away. Substituting,
Therefore, the difference in time is
10 parsecs<span>Another way to look at this is that the apparent magnitude (brightness from true distance) is brighter than the absolute magnitude (brightness from 10 parsecsaway). So Ross 128 must be closer than 10 parsecs, making star look brighter than it "really" is.</span>