Why does the angle of a light ray change when passing through different materials?

When a ray of light passes through materials with different refractive indices, such as from air to glass, the direction of the light changes. This change in direction is known as refraction. Refraction occurs because the speed of light changes as it moves from one medium to another.

The angle at which a ray of light strikes the glass pane on one side is known as the angle of incidence. The angle at which it exits the glass pane on the other side is called the angle of refraction. When the light travels from air into glass, for example, the speed of light decreases in the denser medium of the glass, causing the light to bend.

This change in direction is quantified by Snell's Law, which relates the angles of incidence and refraction to the refractive indices of the two materials. The greater the difference in refractive indices between the two materials, the larger the angle change of the light ray.

Therefore, when the glass pane is made of a different material than the medium the light is coming from, the angle at which the light strikes and exits the pane will be different due to the refraction process. This phenomenon is essential in various applications, such as lenses, prisms, and fiber optics.