Here's why:

* Speed of Light: Light travels slower in denser mediums (like glass or water) compared to less dense mediums (like air).

* Snell's Law: This law describes the relationship between the angle of incidence (the angle at which light hits the surface) and the angle of refraction (the angle at which light bends). It states:

* n₁sinθ₁ = n₂sinθ₂

* n₁ and n₂ are the refractive indices of the two mediums (higher refractive index means denser medium)

* θ₁ and θ₂ are the angles of incidence and refraction, respectively

* Bending Towards the Normal: Since the speed of light is slower in the denser medium, the angle of refraction (θ₂) is smaller than the angle of incidence (θ₁). This means the light ray bends towards the normal, which is an imaginary line perpendicular to the surface at the point of incidence.

Think of it like this: Imagine you're walking from a sidewalk (less dense) onto grass (denser). Your speed will slow down on the grass, and you'll naturally adjust your direction slightly towards the normal (the imaginary line perpendicular to the edge of the sidewalk).