Final answer:
Refraction is the bending of light waves as they pass from one medium to another, due to a change in speed that is influenced by the mediums' differing densities. This results in the light bending towards or away from the normal line, which is described by the law of refraction or Snell's Law.
Step-by-step explanation:
Refraction is the bending of light as it passes from one medium to another. This bending occurs because light waves change speed when they enter a medium with a different density. When light enters a denser medium, it slows down and bends towards the normal line; conversely, it speeds up and bends away from the normal when it moves to a less dense medium. This effect can be observed when light enters or exits surfaces such as water, glass, or air, which have different refractive indices.
The law of refraction, also known as Snell's Law, explains that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant, and is equivalent to the ratio of the indices of refraction of the two media. The degree of bending that occurs is dependent on the properties of the materials and their respective indices of refraction. A familiar example of refraction is a straw appearing bent when it is placed in a glass of water due to the change in the light's direction as it moves from the water to the air.