The inverse square law of light describes how a star's luminosity can be related to its apparent brightness. If Star A has 4 times the apparent brightness of Star B, which of the following could be a valid explanation?
1) Star A and Star B have the same luminosity and distance, but Star A is 4 times hotter than Star B.
2) Star A has 4 times the luminosity of Star B, and is 4 times as far away.
3) Star A and Star B are the same distance away, but Star A emits a higher frequency wavelength of light.
4) Star A and Star B have different chemical compositions.
5) Star A and Star B are the same distance away, but Star A has 4 times the luminosity of Star B.