The time it takes for light to travel from point A to point B and then back to point A again depends on the distance between A and B.
If we assume that the distance between A and B is d, then the total distance traveled by light would be 2d (from A to B and then back to A).
The speed of light in a vacuum is approximately 299,792,458 meters per second.
Using these values, we can calculate the time it takes for light to travel from A to B and back to A using the formula:
Time = Distance / Speed
So, the time it takes for light to travel from A to B and back to A would be:
Time = (2d) / (299,792,458 m/s)
It's important to note that this calculation assumes an idealized scenario where the speed of light remains constant and the distance is measured in a straight line without any obstructions or interactions that could affect the speed of light. In practice, various factors such as the medium through which light travels, gravitational fields, and other effects could slightly modify the actual time taken.