Here's why:

* Speed of light: Light travels faster in a rarer medium than in a denser medium.

* Refraction: When light passes from one medium to another, it changes direction. This bending of light is called refraction.

* Normal: The normal is an imaginary line perpendicular to the surface separating the two media at the point where the light ray strikes the surface.

The bending away from the normal occurs because the light ray speeds up as it enters the rarer medium.

Example:

Imagine a light ray traveling from water (denser) to air (rarer). The light ray will bend away from the normal as it enters the air, causing it to appear to "bend" upwards.