refraction

[ ri-frak-shuhn ]

noun

1. Physics. the change of direction of a ray of light, sound, heat, or the like, in passing obliquely from one medium into another in which its wave velocity is different.
2. Ophthalmology.
   1. the ability of the eye to refract light that enters it so as to form an image on the retina.
   2. the determining of the refractive condition of the eye.
3. Astronomy.
   1. Also called astronomical refraction. the amount, in angular measure, by which the altitude of a celestial body is increased by the refraction of its light in the earth's atmosphere, being zero at the zenith and a maximum at the horizon.
   2. the observed altered location, as seen from the earth, of another planet or the like due to diffraction by the atmosphere.

refraction

/ rɪˈfrækʃən /

noun

1. physics the change in direction of a propagating wave, such as light or sound, in passing from one medium to another in which it has a different velocity
2. the amount by which a wave is refracted
3. the ability of the eye to refract light
4. the determination of the refractive condition of the eye
5. astronomy the apparent elevation in position of a celestial body resulting from the refraction of light by the earth's atmosphere

refraction

/ rĭ-frăk′shən /

1. The bending of a wave, such as a light or sound wave, as it passes from one medium to another medium of different density. The change in the angle of propagation depends on the difference between the index of refraction of the original medium and the medium entered by the wave, as well as on the frequency of the wave.
2. Compare reflectionSee also lens
3. The apparent change in position of a celestial body caused by the bending of light as it enters the Earth's atmosphere.

refraction

1. A change of direction that light undergoes when it enters a medium with a different density from the one through which it has been traveling — for example, when, after moving through air, it passes through a prism . ( Compare reflection .)

Notes

Lenses and other optical instruments work through refraction of light.

Other Words From

• re·fraction·al adjective
• nonre·fraction noun
• nonre·fraction·al adjective

Word History and Origins

Origin of refraction¹

First recorded in 1570–80, refraction is from the Late Latin word refrāctiōn- (stem of refrāctiō ). See refract, -ion

Usage

The terms refraction and reflection describe two ways that waves, as of sound or light, change course upon encountering a boundary between two media. The media might consist of two different substances, such as glass and air, or a single substance in different states in different regions, such as air at different temperatures or densities in different layers. Reflection occurs, as in a mirror, when a wave encounters the boundary but does not pass into the second medium, instead immediately changing course and returning to the original medium, typically reflecting from the surface at the same angle at which it contacted it. Refraction occurs, as in a lens, when a wave passes from one medium into the second, deviating from the straight path it otherwise would have taken. The amount of deviation or “bending” depends on the indexes of refraction of each medium, determined by the relative speed of the wave in the two media. Waves entering a medium with a higher index of refraction are slowed, leaving the boundary and entering the second medium at a greater angle than the incident wave. Waves entering a medium with a lower index are accelerated and leave the boundary and enter the second medium at a lesser angle. Incident light waves tend to be fully reflected from a boundary met at a shallow angle; at a certain critical angle and at greater angles, some of the light is also refracted; looking at the surface of water from a boat, for instance, one can see down into the water only out to where the sight line reaches the critical angle with the surface. Light passing through a prism is mostly refracted, or bent, both when it enters the prism and again when it leaves the prism. Since the index of refraction in most substances depends on the frequency of the wave, light of different colors is refracted by different amounts—hence the colorful rainbow effect of prisms. The boundary between media does not have to be abrupt for reflection or refraction to occur. On a hot day, the air directly over the surface of an asphalt road is warmer than the air higher up. Light travels more quickly in the lower region, so light coming down from the sky (from not too steep an angle) is refracted back up again, giving a “blue puddle” appearance to the asphalt—a mirage.

Example Sentences

This is called a 'Fresnel lens' or 'zone plate lens', and it focuses light using diffraction rather than refraction.

From Science Daily

However, one drawback is that this field weakens inside the material due to light refraction at the air-material interface, limiting its use.

From Science Daily

The phenomenon is caused by the refraction of moonlight from ice crystals in the upper atmosphere.

From BBC

This information and the ways it can be an analog or a refraction of an American reality may not be new, but 20 years on it's perhaps easier to realize how visceral it all is.

From Salon

On the right, meanwhile, the precariously balanced melons encroach on this central duo, their knobbly, green-and-yellow skins — so different from the bottle and glass! — creating a colored refraction in the clear water.

From Washington Post