Definitions for critical angle
Random House Webster's College Dictionary
crit′ical an′gle(n.)
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.
Category: Optics
the angle of attack at which a sudden change in airflow occurs around the wings of an aircraft, reducing lift and increasing drag.
Category: Aeronautics
Origin of critical angle:
1870–75
Princeton's WordNet
critical angle(noun)
the smallest angle of incidence for which light is totally reflected
Wiktionary
critical angle(Noun)
The smallest angle of incidence for which light is totally reflected from a boundary between one medium and a less refractive one
critical angle(Noun)
The smallest angle of attack of an airfoil at which lift suddenly decreases and drag suddenly increases
critical angle(Noun)
The smallest angle of a ramp or stairs considered uncomfortable or unsafe
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"critical angle." Definitions.net. STANDS4 LLC, 2013. Web. 23 May 2013. <http://www.definitions.net/definition/critical angle>.

