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critical angle

noun
1.
Optics. the minimum angle of incidence beyond which total internal reflection occurs for light traveling from a medium of higher to one of lower index of refraction; the angle of incidence for which refracted rays emerge tangent to the surface separating two media, the light traveling from the medium of higher to the medium of lower index of refraction.
2.
Also called angle of stall, critical angle of attack, stalling angle. Aeronautics. the angle of attack, greater than or equal to the angle of attack for maximum lift, at which there is a sudden change in the airflow around an airfoil with a subsequent decrease in lift and increase in drag.
Origin
1870-1875
1870-75
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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British Dictionary definitions for critical-angle

critical angle

noun
1.
the smallest possible angle of incidence for which light rays are totally reflected at an interface between substances of different refractive index
2.
another name for stalling angle
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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critical-angle in Science
critical angle
  (krĭt'ĭ-kəl)   
The smallest angle of incidence at which radiation, such as light, is completely reflected from the boundary between two media. At angles smaller than the critical angle, some of the radiation enters the second material and is refracted.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Article for critical-angle

critical angle

in optics, the greatest angle at which a ray of light, travelling in one transparent medium, can strike the boundary between that medium and a second of lower refractive index without being totally reflected within the first medium. (The refractive index of a transparent substance is the ratio of the speed of light in a vacuum to its speed in that substance.) For any angle of incidence smaller than the critical angle, and for any angle at all if the ray strikes the boundary from the other side, part of the beam will penetrate the boundary, being refracted in the process.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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