Two distant stars are observed through a telescope. Star A is observed to be half as bright as star B. Star A is calculated to be twice as far away as star B.
Obviously this involves the equation:
F=4πd2LWhere F is the received or perceived brightness (Flux).
So we have:
2Fa=Fb∴Fa=21Fb.
And so:
da22La=db2Lb.
Is that it?
Doesn't the distance come into it? Why not? Is it because it is 'calculated' distance? So, presumably, that distance comes from the above observation?
The answer is Star A has twice the luminosity of Star B.