Star A and star B appear equally bright in the sky.Star A is twice as far away from Earth as star B.How do the luminosities of stars A and B compare?
A) Star A is twice as luminous as star B.
B) Star B is twice as luminous as star A.
C) Star A is four times as luminous as star B.
D) Star B is four times as luminous as star A.
E) Stars A and B have the same luminosity.

Question

Quizplus · Accepted Answer

The apparent brightness of a star is inversely proportional to the square of its distance. Since star A is twice as far as star B but appears equally bright, it must be four times more luminous to compensate for the increased distance.

Star a and Star B Appear Equally Bright in the Sky.Star