When light travels from one medium to another, its direction
can change. This is called

Newtons law of gravitation is called the universal law of gravitation because it is applicable for all masses at all distances, independent of the medium.

Explanation:

For two masses m1 and m2 placed at a distance d, the gravitational force between them will always be given by: Fg=Gd2m1m2. That's why it is a "universal" law.