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

One of the challenges with this approach, Lake said, is making this light refraction work with curved lenses. —Lauren Goode, WIRED, 23 Oct. 2018

Powerful ray tracing that provides more dynamic reflection and refraction of light. —Erik Kain, Forbes, 11 Sep. 2024

The apparent equal hours of daylight and darkness result from the refraction of sunlight, or the bending of light's rays, the National Weather Service reports. —Olivia Munson, USA TODAY, 8 Sep. 2024

The exam includes visual acuity tests that evaluate how each eye can see (e.g., reading charts) and a refraction test. —Lindsay Curtis, Health, 18 Aug. 2024

Word History

First Known Use

1603, in the meaning defined at sense 1

Phrases Containing refraction

• angle of refraction
• double refraction
• index of refraction

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