Visual Optics Practice Test

When light enters a medium with a higher refractive index, the speed of light decreases. The refractive index of a medium is defined as the ratio of the speed of light in a vacuum to the speed of light in that medium. Thus, when light transitions from a less optically dense medium (like air) to a more optically dense medium (like glass or water), its speed diminishes due to the interaction of light with the material's molecules.

This change in speed also affects how light bends as it passes into the new medium. The greater the refractive index of the second medium, the more significant the reduction in speed, leading to a greater degree of bending. Understanding this principle is fundamental in optics as it plays a key role in phenomena such as refraction, which governs how lenses and prisms function.