When a light wave passes from a less dense medium like air into a more dense medium like glass, it undergoes refraction, which means it bends. Here's a breakdown of what happens:

* Speed Change: Light travels slower in denser mediums. So, as the light wave enters the glass, its speed decreases.

* Angle Change: Because of the speed change, the direction of the light wave also changes. The light ray bends towards the normal. The normal is an imaginary line perpendicular to the surface of the glass at the point where the light enters.

Key Points:

* Refraction: The bending of light as it passes from one medium to another.

* Normal: An imaginary line perpendicular to the surface of the medium.

* Angle of Incidence: The angle between the incident ray (light entering the medium) and the normal.

* Angle of Refraction: The angle between the refracted ray (light exiting the medium) and the normal.

Snell's Law: The relationship between the angles of incidence and refraction is described by Snell's Law:

n1 * sin(θ1) = n2 * sin(θ2)

where:

* n1 and n2 are the refractive indices of the two mediums (air and glass).

* θ1 is the angle of incidence.

* θ2 is the angle of refraction.

In summary, when light passes from air to glass, it bends towards the normal because it slows down.