Final answer:
Snell's law, expressed as n1 sin θ1 = n2 sin θ2, describes how light waves bend when entering different media due to changes in phase velocity, associated with the medium's refractive index.
Step-by-step explanation:
Snell's law states the relationship between the angles of incidence and refraction when a light wave passes from one medium into another. Formally, it is expressed as n1 sin θ1 = n2 sin θ2, where n1 and n2 are the indices of refraction for the respective media, and θ1 and θ2 are the angles the ray makes with the normal to the interface in each medium. This law showcases how the speed of light and the wavelength are related to the refractive index of the material.
Derived from Huygens's principle, the law indicates that when light enters a medium with a higher index of refraction (thus lower speed of light), it bends towards the normal, and when it enters a medium with a lower index of refraction (higher speed), it moves away from the normal.
The phase velocity of light changes when transitioning between media which contributes to the refraction observed according to Snell's law. Moreover, Einstein's theory of special relativity confirms that the speed of light in a vacuum, denoted by c, is a constant and not dependent on the relative motion of the observer, contrasting with classical predictions made by Newton's laws.