refraction

noun

re·​frac·​tion ri-ˈfrak-shən 

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

• a light ray
• b reflected ray
• c refracted ray

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

If Earth’s atmosphere were perfectly static and homogeneous, then the refraction of starlight would be minimal. —Phil Plait, Scientific American, 15 May 2025

As the sun rises, rainbow refractions appear along the web strands. —Cecilia Rodriguez, Forbes.com, 18 Apr. 2025

The process, called subjective refraction, involves the patient comparing lens options while their eye's focusing system and brain interpret the clarity of each one. —Dan Perry, Newsweek, 31 Jan. 2025

Avoiding reflection or refraction in the the cooling liquid also required making the fluid flow smoothly through the channels to prevent turbulence. —IEEE Spectrum, 21 Oct. 2020

Word History

First Known Use

1603, in the meaning defined at sense 1

Phrases Containing refraction

• angle of refraction
• double refraction
• index of refraction

Rhymes for refraction

• abstraction
• attraction
• compaction
• contraction
• detraction
• diffraction
• distraction
• exaction
• extraction
• impaction
• inaction
• infraction

Kids Definition

refraction

noun

re·​frac·​tion ri-ˈfrak-shən 

: 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)

refractive

-ˈfrak-tiv

adjective

Medical Definition

refraction

noun

re·​frac·​tion ri-ˈfrak-shən 

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

2

a

: 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