What happens to light when it enters a medium that is denser than the one it came from?

When light enters a denser medium, such as from air into water or glass, it experiences a change in speed due to the differing optical densities of the two materials. This change in speed causes the light to bend, and it specifically bends towards the normal, which is an imaginary line that is perpendicular to the surface at the point of entry.

The reason light bends towards the normal in a denser medium is rooted in the principle of refraction, described by Snell's Law. As light travels from a less dense medium to a denser one, its velocity decreases, leading to the change in direction towards the normal line. This bending effect is significant in various practical applications, such as the design of lenses in optical instruments, where controlling the path of light is crucial for obtaining clear images.

In contrast, the other options do not accurately describe the behavior of light in this scenario. Dispersal or reflection may occur under different circumstances, but they do not pertain specifically to the interaction of light as it passes into a denser medium. Understanding this principle is fundamental in explaining phenomena related to light behavior in various environments.