Final answer:
Refraction is the change in direction of a light ray when it passes from one medium to another due to variations in light speed across materials with different refractive indices. This bending of light is responsible for many optical effects and is described by the Law of Refraction.
Step-by-step explanation:
Refraction of Light
The change in direction of a light ray when it passes from one substance into another, such as from water into air, is known as refraction. This phenomenon occurs due to variations in the speed of light as it travels through different materials with different refractive indices. When a light ray enters a substance with a higher index of refraction, it slows down and bends towards the normal (the perpendicular line to the surface at the point of entry); conversely, upon entering a substance with a lower index of refraction, the light speeds up and bends away from the normal. This behavior underlies various optical phenomena, from the functioning of lenses to the transmission of signals through optical fibers.
Refraction is directly related to the factors that affect the speed of light, including the density and composition of the materials it encounters. The Law of Refraction, also known as Snell's Law, mathematically describes this directional change based on the indices of refraction of the two media involved. Additionally, refraction explains why objects under water appear shifted from their actual position when viewed from above the surface.