Two blinking warning lights are $1000 \mathrm{~ns}$ apart along a railroad track. A train moves from west to east at a speed of 0.5 . In the train frame, an observer registers flashes from each light, and after correcting for light travel time, concludes that the east light flashed 200 ns before the west light flashed. Which light flashed first in the ground frame? (Hint: Draw a space time diagram.)
A) The east light flashes before the west light.
B) The west light flashes before the east light.
C) The lights flash simultaneously.
D) One does not have enough information to say.

Question

Quizplus · Accepted Answer

Given that in the train frame, after correcting for light travel time, the east light is observed to have flashed 200 ns before the west light, it implies that in the ground frame, the west light must have flashed first. This is because the train is moving towards the east light, making it seem like the east light flashed earlier due to the relative motion between the train and the lights.

Two Blinking Warning Lights Are 1000 ns1000 \mathrm{~ns}1000 ns Apart Along a Railroad Track

Two Blinking Warning Lights Are $1000 \mathrm{~ns}$ Apart Along a Railroad Track