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Refraction is the bending of light as it passes between materials of different optical density.
Definition: Index of Refraction
Index of Refraction of a material is the ratio of the speed of light in vacuum to the speed of light in that material:
Idea: Explanation for Refraction of Light
The change in speed and wavelength at the boundary between two materials causes light to change direction. Think of a car approaching a patch of mud at a sharp angle from a well paved road. The tire that hits the mud first will slow down, while the other tire is still going fast on the good road. This will cause the car to turn, until both tires are in the mud and going at the same speed. If is the angle of the ray relative to the normal to the surface in medium 1, and is the angle relative to the normal in medium 2, then:
|= = =||(3)|
For a light ray passing from a more dense to a less dense material, there is a critical angle of incidence for which the angle of refraction is 90 o . For greater angles of incidence, the light cannot pass through the boundary between the materials, and is reflected within the more dense material. For a light ray trying to pass from medium 2 to medium 1, the critical angle is given by:
sin = sin 90 o =where n1 is the index of refraction of the less dense material, and n2 is the index of refraction of the more dense material.