* Refraction is the bending of light as it passes from one medium to another. This bending occurs because the speed of light changes in different media.

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

* The rule: When light travels from a less dense medium (like air) to a denser medium (like water or vegetable oil), the refracted ray bends towards the normal.

Why?

Light travels slower in denser media. When light enters a denser medium, it slows down and changes direction. This change in direction results in the refracted ray bending towards the normal.

In summary:

* Light refracts towards the normal when going from air to water.

* Light refracts towards the normal when going from air to vegetable oil.