Refraction - water or glass to air
When light travels at an angle from water or glass to air the light speeds up and changes direction. The light turns away from the normal line.
Think of it as a tractor moving from a slow muddy, grassy field onto a fast moving road.
The first wheel hits the fast road and starts to speed up. The other side is still slipping in the mud. This starts to make the tractor speed up and change direction.
(This is the same for light waves or water waves)
Light rays travel at 226,000km/s through water but when the light again reaches the air it will travel back up to 300,000km/s.
The same effect occurs from glass to air.
When light enters a less dense substance (a lower refractive index) it bends away from the normal line.