Here's why:

* Refraction: This is the phenomenon of light bending as it passes from one medium to another. The bending occurs because light travels at different speeds in different mediums.

* Denser Medium: A denser medium means light travels slower in that material.

* Normal: The normal is an imaginary line perpendicular to the surface where the light enters the new medium.

How it Works:

1. When light enters a denser medium (like from air to water), it slows down.

2. The part of the light wave that hits the denser medium first slows down before the rest of the wave.

3. This causes the wavefront to change direction, bending towards the normal.

Think of it like this: Imagine you're walking from a sidewalk onto a muddy field. Your foot on the sidewalk moves faster than your foot in the mud. This causes your body to shift direction slightly, just like the light wave!