Definition of "refraction" [re•frac•tion]

• The turning or bending of any wave, such as a light or sound wave, when it passes from one medium into another of different optical density. (noun)
• Astronomy The apparent change in position of celestial objects caused by the bending of light rays entering Earth's atmosphere. (noun)
• Medicine The ability of the eye to bend light so that an image is focused on the retina. (noun)
• Medicine Determination of the refractive characteristics of the eye. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• ""I did not leave untried," says he, "whether, by assuming a horizontal refraction according to the density of the medium, the rest would correspond to the sines of the distances from a vertical direction, but calculation proved that it was not so: and, indeed, there was no occasion to have tried it, for thus the _refraction would increase according to the same law in all mediums, which is contradicted by experiment_.""
• "The offside lamp pointing forward should be covered with a handkerchief, to diffuse the light and cause less refraction from the fog in front."
• "Any gas would work, although helium's index of refraction is extremely low."