critical angle

American  

[krit-i-kuhl ang-guhl] / ˈkrɪt ɪ kəl ˈæŋ gəl /

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,.  Also called stalling angle.  Also called critical angle of attack;.  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.

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critical angle British  

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

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critical angle Scientific  

/ krĭt′ĭ-kəl /

1. 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.

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Etymology

Origin of critical angle

First recorded in 1870–75

Example Sentences

However, at a critical angle, the forces keeping the sandpile together yield to gravity: the pile breaks down and starts flowing, acting like a liquid.

From Science Daily • Nov. 25, 2024

The critical angle reported by subjects depended upon whether Kevin was blindfolded.

From Scientific American • Dec. 29, 2020

As the airplane approaches that critical angle, the first event is a stall warning in the cockpit.

From New York Times • Sep. 18, 2019

The critical angle for a diamond-to-air surface is only 24.4º , and so when light enters a diamond, it has trouble getting back out.

From Textbooks • Aug. 12, 2015

The thin-faced veteran in the slouch hat plunged his hands deeper into his trousers' pockets, and, turning his head to a critical angle, said patronizingly to the ice-man: "Them's the things they calls 'tally-ho's.'"

From With Edge Tools by Chatfield-Taylor, H. C. (Hobart Chatfield)