Question

MUST ANSWER EVERY PART

In each of the following situations, Emma is in the exact center of a glass-sided fright car speeding to the right at a very high speed v relative to you. For each question, explain your reasoning.

Emma has a flashlight in each hand and directs them at the front and rear ends of the freight car. She then switches the flashlights on at the same time.

In Emma�s frame of reference, which beam of light travels at a greater speed, the one directed toward the front or the one directed toward the rear of the train, or do they travel at the same speed?

In Emma�s frame of reference, which end, front or rear, is struck by light first, or are they struck at the same time? Which end is struck first in your frame of reference?

Answer 1

1) According to the second postulated of special theory of relativity, The speed of light in free space has the same value c in all inertial frames of reference. ie, As measured in any inertial frame of reference, light is always propagated in empty space with a definite velocity c that is independent of the state of motion of the emitting body

So both the light, one direcrted towards the front and one directed towards the rear end will travel at the same speed in Emma's frame of reference.

2) As Emma is sitting in the exact centre of the car, the distance from flash light and both the ends are same. Velocity of light is constant c and distances are same, hence, in Emma's frame of reference, both front end and rear end stuck by light at the same time. In our frame of reference ( external viewer) also, both the front end and rear end struck by light at the same time as the freight car moves with a constant velocity with respect to our frame.