critical angle


critical angle
i. The minimum angle of incidence at which a radio wave of a particular frequency can strike the ionosphere and still be reflected back to the earth. Critical angle is a function of frequency; the higher the frequency, the larger the critical angle.
If radio wave hits the ionosphere at an angle higher than critical angle, it would not be reflected back, but will pass through the ionosphere into space.
ii. The angle of attack of an airfoil at which the flow of air about the airfoil changes abruptly in such a manner that the lift is sharply reduced and the drag is sharply increased. Sometimes called stalling angle of attack.
iii. The angle at which a reflected ray of light when transmitted from a denser to a rarer medium is bent so far from the normal that it does not enter the rarer medium at all but travels parallel to the surface between the media.
iv. The angle of bank beyond which a helicopter resting on the ground on one skid or one wheel is likely to roll over in an uncontrolled manner.
At the instant of rollover of a helicopter, a moment is produced by the horizontal component of total rotor thrust about the point of ground contact of the skid. This moment is opposed by weight of the aircraft. If the angle of bank is beyond the critical angle the restoring moment is too small to stop the helicopter from rolling over.

Aviation dictionary. 2014.

Look at other dictionaries:

  • Critical angle — Critical Crit ic*al (kr[i^]t [i^]*kal), a. [See {Critic}, n., {Crisis}.] [1913 Webster] 1. Qualified to criticise, or pass judgment upon, literary or artistic productions. [1913 Webster] It is submitted to the judgment of more critical ears to… …   The Collaborative International Dictionary of English

  • Critical angle — can refer to: Critical angle (optics) the angle of incidence above which total internal reflection occurs Critical angle of attack, in aerodynamics; the angle of attack which produces the maximum lift coefficient Critical angle of repose, in… …   Wikipedia

  • critical angle — n. 1. Optics the smallest possible angle of incidence at which light rays are totally reflected 2. Aeron. that angle of attack at which the flow of air around an airfoil suddenly changes, with an abrupt reduction in lift and an increase of drag:… …   English World dictionary

  • critical angle — 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 …   Universalium

  • critical angle — ribinis kampas statusas T sritis fizika atitikmenys: angl. critical angle vok. Grenzwinkel, m rus. предельный угол, m pranc. angle critique, m; angle limite, m …   Fizikos terminų žodynas

  • critical angle — kritinis kampas statusas T sritis fizika atitikmenys: angl. critical angle vok. kritischer Winkel, m rus. критический угол, m pranc. angle critique, m …   Fizikos terminų žodynas

  • critical angle — noun the smallest angle of incidence for which light is totally reflected • Hypernyms: ↑angle of incidence, ↑incidence angle …   Useful english dictionary

  • critical angle — noun a) The smallest angle of incidence for which light is totally reflected from a boundary between one medium and a less refractive one b) The smallest angle of attack of an airfoil at which lift suddenly decreases and drag suddenly increases …   Wiktionary

  • critical angle — crit′ical an′gle n. 1) opt 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 2) aer. the angle of attack at which a sudden change in… …   From formal English to slang

  • critical angle — /ˌkrɪtɪkəl ˈæŋgəl/ (say .kritikuhl angguhl) noun 1. Optics the limiting angle of incidence for total internal reflection. 2. the angle of attack at which there is a sudden change in the airflow round an aerofoil with subsequent decrease in lift… …   Australian English dictionary


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