Suppose that two identical stars (they have the same total light output) are located so that star A is at a distance of 5 pc, and star B is at a distance of 25 pc from Earth. How will star B appear, compared with star A?
A) Star B will be 1/5 as bright as star A.
B) Star B will be 1/25 as bright as star A.
C) Star B will be 1/2.2 as bright as star A.
D) Star B will be 1/20 as bright as star A.

Question

Quizplus · Accepted Answer

The brightness of a star is inversely proportional to the square of its distance. Since star B is 5 times farther than star A, it will appear (1/5)^2 = 1/25 as bright as star A.

Suppose That Two Identical Stars (They Have the Same Total