What happens when a parallel beam of light enters a rectangular glass block? Assuming the light exits the block along the side opposite to the side it entered, what path does the light follow when it emerges from the block?

1. The exact path it was following when it entered the block.
2. A path parallel to the original path, but displaced from it.
3. A path perpendicular to the original path.
4. None of the above.

The path is parallel to the original path. In general it is displaced from the original path. The only case when it is not displaced is when the light strikes the block perpendicular to the surface.