A star is moving towards the earth with a speed at 90% the speed of light.It emits light,which moves away from the star at the speed of light.Relative to us on earth,what is the speed of the light moving toward us from the star?
A) 0.90c
B) c
C) 1.1c
D) 1.20c
E) 1.9c

Question

Quizplus · Accepted Answer

The speed of light is constant, regardless of the motion of the source or the observer. Therefore, the light emitted from the star will always move away from it at the speed of light, which is "c." The fact that the star is moving towards us at 90% the speed of light does not affect the speed of the light emitted by the star moving towards us. Therefore, the speed of light moving towards us from the star is also "c."

A Star Is Moving Towards the Earth with a Speed