No, refraction occurs regardless of the angle at which light rays hit a surface.

Here's why:

* Refraction is the bending of light as it passes from one medium to another. This happens because the speed of light changes in different mediums (like air, water, glass).

* The angle at which the light hits the surface determines the amount of bending. If light hits the surface at a perpendicular angle (straight up and down), there's no bending. However, if the light hits at an angle, it bends towards or away from the normal line (an imaginary line perpendicular to the surface).

So, refraction doesn't depend on the light being straight up and down, but on the change in speed of light as it crosses the boundary between two mediums.