Stars A and B appear equally bright, but star A is twice as far away from us as star B. Which of the following is true?
A) Star A is twice as luminous as star B.
B) Star A is four times as luminous as star B.
C) Star B is twice as luminous as star A.
D) Star B is four times as luminous as star B.
E) Star A and star B have the same luminosity because they have the same brightness.

Question

Quizplus · Accepted Answer

Star A is twice as far away, so it must be four times as luminous as star B to appear equally bright, due to the inverse square law of light.

Stars a and B Appear Equally Bright, but Star a Is