critical angle


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critical angle:

see refractionrefraction,
in physics, deflection of a wave on passing obliquely from one transparent medium into a second medium in which its speed is different, as the passage of a light ray from air into glass.
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critical angle

[′krid·ə·kəl ¦aŋ·gəl]
(architecture)
The angle of pitch of a flight of stairs or a ramp that, if exceeded, is considered uncomfortable and unsafe; it is 50° for stairs and 20° for ramps.
(physics)
An angle associated with total reflection of electromagnetic or acoustic radiation back into a medium from the boundary with another medium in which the radiation has a higher phase velocity; it is the smallest angle with the normal to the boundary at which total reflection occurs.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

critical angle

An angle of pitch of stairs or a ramp which is considered uncomfortable and unsafe if exceeded; this angle is 50° for stairs and 20° for ramps.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.

critical angle

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.
critical angle
critical angleclick for a larger image
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.
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.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved

critical angle

In an optical fiber, the maximum angle from the axis at which light can remain confined within the core for "total internal reflection." In contrast to the "acceptance angle," which is measured outside the fiber, the critical angle is a measurement within the fiber. See numerical aperture.
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References in periodicals archive ?
Based on theoretical investigation it is necessary to define the geometry of the light guide, it is known that the starting point has to be such, that the incidence light from the source would have incidence angle inside the light guide equal to critical angle for total internal reflection to take place and for the system to be in equilibrium.
We see that there is no critical angle in this case for all incident angles from air such that the wave never experiences TIR back into air.
Figure 5 presents the dependence [bar.[i.sub.0]] = f([bar.i']), the analysis of which demonstrates that hysteresis by critical angle of attack occurs in different values of inability to calculate the flow at [bar.i'] > 1.
At a certain crack width, w, only those fibres which are inclined less than the critical angle [[theta].sub.crit] can be taken in to account.
2.4 DEVELOPMENT OF OPTICAL DESIGN ALGORITHM IN CONSIDERATION OF CRITICAL ANGLE AND DIFFUSE LIGHT
CANCER (June 22-July 23) You seem to be looking at yourself from an overly critical angle and it would be worth your while accepting and taking in some of the constructive comments that your close ones are giving you.
For me, this was the frustration of the study; I was always looking for a more critical angle, or a conversation with current philosophical voices.
The National Transportation Safety Board is not confirming that sewer work could have increased the risk of an explosion, but the agency is also looking at this critical angle as it continues its investigation.
Our side-to-side motion became more erratic until we reached a critical angle that tipped the canoe, which sank like a stone and had to be righted and baled.
It can be found that in all the Reynolds number, the lift coefficient of seagull airfoil is more than that of the NACA 4412 airfoil and at higher Reynolds numbers (Re=3.5' [10.sup.5] and 6' [10.sup.5]), the seagull airfoil's critical angle of incidence [a.sub.c] is 14[degrees], while the [a.sub.c] of NACA 4412 airfoil is 12[degrees].

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