A (very long) mirror is moving from left to right at 0.5c and we point a laser at it perpendicularly as it passes in front of us. (it glides in its own plane, like the windows of a train)
How will the laser bounce off the mirror? will it follow the original path back to the source, in the same manner as if the mirror was at rest? or will it reflect at an angle?
Clarification: let's consider the mirror as being front surface, to avoid discussing about light traveling through a layer of glass or anything similar. The point of the question is simply about reconciling the fact that different reference frames point to different results.
EDIT: The reason I asked the question is because from the source's perspective it would appear the movement of the mirror is irrelevant. However, for the reflected ray we can also consider the mirror as being the source, which means the light would go straight in the mirror's reference frame, meaning oblique for the outside observer.