The Physics Factbook
Edited by Glenn Elert -- Written by his students
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|Serway, Raymond., Faughn, Jerry S. "The Law of Refraction." College Physics. Sixth edition, Pacific Grove, CA: Brooks/Cole-Thomson Learning, 2003: 692.||"Indices of Refraction for Various Substances, Measure with Light of Vacuum Wavelength 589nm … Air 1.000293"||1.000293|
|Encarta. Indexes of Refraction. Microsoft 2005.||"Substance Refractive Index … Air 1.0003"||1.0003|
|Lide, David R. "Index of Refraction of Air." Handbook of Chemistry and Physics. 75th edition. Boca Raton, FL, CRC Press Inc., 1994: 10-302.||
|Selloy, Samuel M. "Index of Refraction of Air." Handbook of Chemistry and Physics. 48th edition, Cleveland OH, The Chemical Rubber Co., 1967: E-160.||[table]||1.0002000-1.0002739|
|Weisstein Eric. Index of Refraction. Wolfram Research. 2005.||"Index of Refraction … Air 1.00029"||1.00029|
For thousands of years, people have noted that a straight stick placed in water appears to be broken at an angle where it enters the water. This is the origin of the term "refraction,'' which means "broken back.''
Every material that light can travel through has an index of refraction, denoted by the letter n. The velocity of light in a vacuum is 3.0 × 108 m/s. The index of refraction equals the ratio of the velocities of light in vacuum (c) to that in the medium (v), that is n = c/v. Light slows down when traveling through a medium, thus the index of refraction of any medium will be greater than one. The index of refraction of air is 1.0003, which is very similar to the index of refraction in a vacuum (1.0000), therefore, in most problems, these indices are used interchangeably. The index of refraction is also based on the wavelength of the incident light, where light of a longer wavelength refracts less than light of a shorter wavelength.
The actual law of refraction was discovered in the early 1600s by a Dutch mathematician and geodesist, Willebrord Snell van Royen, which is now termed Snell's law. When light is refracted at a surface, the angles of the incident and refracted rays are related by Snell's law, n1sinθ1 = n2sinθ2. n represents the refractive indices of material 1 and material 2 and are the angles of light traveling through these materials with respect to the normal. The index of refraction of air, along with other materials is essential to many optics and laser applications.
Maya Barsky -- 2005
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