re·​frac·​tion | \ri-ˈfrak-shən \

Definition of refraction 

1 : deflection from a straight path undergone by a light ray or energy wave in passing obliquely from one medium (such as air) into another (such as glass) in which its velocity is different

2 : the change in the apparent position of a celestial body due to bending of the light rays emanating from it as they pass through the atmosphere also : the correction to be applied to the apparent position of a body because of this bending

3 : the action of distorting an image by viewing through a medium also : an instance of this

Illustration of refraction

Illustration of refraction

refraction 1: a light ray, b reflected ray, c refracted ray

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Did You Know?

The root of refraction is seen in the notion that the path of a ray of light or wave of energy is "broken" when it is deflected or turned. The effects of refraction can be seen in a rainbow, which is formed when light rays passing into (and reflecting out of) water droplets are bent at different angles depending on their color, so that the light separates into bands of color. The amount of refraction depends on the angle and the type of matter; refraction can occur even when passing through different kinds of air. A mirage, such as you might see in the desert or over a patch of asphalt in the summer, occurs when light passing through warm air meets the very hot air near the surface; reflecting the sky, it often resembles a lake.

Examples of refraction in a Sentence

Recent Examples on the Web

The Medicare program that provides coverage for millions of Americans age 65 and older doesn’t include routine eye exams, refraction testing or eyeglasses. Michelle Andrews, Washington Post, "Lack Of Insurance Exposes Blind Spots In Vision Care," 15 May 2018 Statements from the American Optometric Association and state organizations say that the technology that an app or computer relies on (known as refraction) doesn’t represent a comprehensive survey. John D. Stoll, WSJ, "Can Health Care Be Disrupted? Warby Parker Offers a Clue," 6 July 2018 The high refraction allows for the possibility of making light-manipulating structures on the surface of the sail that contribute to its reflectivity. John Timmer, Ars Technica, "The material science of building a light sail to take us to Alpha Centauri," 7 May 2018 That generally means that those plans cover a comprehensive eye exam, including refraction, every year, as well as a pair of glasses or contact lenses. Michelle Andrews, Washington Post, "Lack Of Insurance Exposes Blind Spots In Vision Care," 15 May 2018 The minerals in the rocks, plus refractions from the sun, create a range of colors under the water, from gold to deep blue. Susan Glaser,, "Iceland Travel Blog: Snorkeling in glacial water between two continents (photos)," 9 May 2018 The location high in the mountains of Chile is desirable because the air is so dry and thin here that atmospheric refraction, which obscures astronomers' views of the cosmos, is less of a hindrance than almost anywhere else on the planet. Jay Bennett, Popular Mechanics, "Extremely Large Telescope Construction Is Under Way in Chile," 7 May 2018 The reflection/refraction of these materials also have to cover a broad range of wavelengths since, once the craft is moving fast enough, the incoming photons will be red-shifted. John Timmer, Ars Technica, "The material science of building a light sail to take us to Alpha Centauri," 7 May 2018 The company makes nanocrystals — specks of zirconia a fraction of the width of a strand of hair — that can be added to polymers and coatings to improve the adhesiveness of specialty glues and improve refraction in LED lights. Christopher Dinsmore,, "Baltimore advanced material maker Pixelligent raises $7.6 million in latest funding round," 18 Apr. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'refraction.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of refraction

1603, in the meaning defined at sense 1

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The first known use of refraction was in 1603

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More Definitions for refraction


re·​frac·​tion | \ri-ˈfrak-shən \

Kids Definition of refraction

: the bending of a ray when it passes at an angle from one medium into another in which its speed is different (as when light passes from air into water)


re·​frac·​tion | \ri-ˈfrak-shən \

Medical Definition of refraction 

1 : the deflection from a straight path undergone by a light ray or a wave of energy in passing obliquely from one medium (as air) into another (as water or glass) in which its velocity is different

2a : the refractive power of the eye

b : the act or technique of determining ocular refraction and identifying abnormalities as a basis for the prescription of corrective lenses

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Comments on refraction

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something that serves to warn or remind

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