What is Refraction?

This article was updated on the 11th September 2019.

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Refraction describes the change in direction of a wave caused by its passing through gradual changes in its medium, or by passing from one medium to another.

When light waves pass from one medium to another, and there is a difference between the materials’ indices of refraction (the speed at which light can travel through the material), then refraction occurs.

A wave of light striking level water vertically (a perpendicular angle of incidence) will not be refracted, but if the beam enters the water any other angle then the light will be refracted relative to the deviation of the angle of incidence from 90 degrees. In other words, the angle of the refracted light proportionally increases with the entry angle of the incident light – the larger the angle of incidence, the greater the bending.

The refraction of visible light is an important characteristic of lenses because the phenomenon causes lenses to focus a wide beam of light onto a narrow point (in the same way as the human eye). By focussing light in this way, lenses can form a magnified image. This enables, for example, telescopes to create an image of a distant object in the eyepiece, or cameras to form a real image on their image sensors.

Source: AZoOptics