A light ray will refract twice when it travels sideways through a glass of water and comes out the other side.

Here's why:

* Refraction 1: When the light ray enters the water from air, it slows down and bends towards the normal (an imaginary line perpendicular to the surface).

* Refraction 2: When the light ray exits the water and enters the air again, it speeds up and bends away from the normal.

So, there are two points where the light ray changes direction due to a change in medium, resulting in two refractions.