What does Snell's Law describe?

Snell's Law describes the relationship between the angle of incidence and the angle of refraction when light passes from one medium to another. It quantitatively expresses how light bends as it enters a different medium, such as air to glass or glass to water. The law states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant and is determined by the indices of refraction of the two media involved. This fundamental principle is essential in understanding how lenses work, the behavior of light in different materials, and many optical devices.

The other aspects listed, such as the angle of reflection, the absorption of light, and the speed of light in a vacuum, do not pertain to the function of Snell's Law, making option B the accurate choice.