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Encyclopedia > Angle of incidence

In any of several scientific and engineering disciplines, the term angle of incidence is used as a measure of deviation from "straight on", for example in the approach of a ray to a surface, or the direction of an airfoil with respect to the direction of an airplane. Image File history File links Angle_of_incidence. ... Image File history File links Angle_of_incidence. ...

## Contents

In optics, an angle of incidence is the angle between a beam incident on a surface and the line perpendicular to the surface at the point of incidence, called the normal. The beam can be formed by any wave: optical, acoustical, microwave, X-ray etc. In Fig. 1 the red line representing a ray makes an angle θ with the normal (dotted line). The angle of incidence at which light is first totally internally reflected is known as the critical angle.The angle of reflection and angle of refraction are other angles related to beams. A surface normal, or just normal to a flat surface is a three-dimensional vector which is perpendicular to that surface. ... This article or section does not cite any references or sources. ... Microwaves are electromagnetic waves with wavelengths longer than those of terahertz (THz) frequencies, but relatively short for radio waves. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... In geometric optics, at a refractive boundary, the critical angle is the angle of incidence above which total internal reflection occurs. ... An angle of incidence is the angle between a beam incident on a surface and the normal (line perpendicular to the surface at the point of incidence). ... Angle of refraction refers to the angle a wave makes to the line of normal incidence when a wave passes from one medium to another. ...

## Alternate terminology

When dealing with a beam that is nearly parallel to a surface, it is sometimes more useful to refer to the angle between the beam and the surface, rather than the beam and the surface normal, $~~pi/2-theta~~$ in the Figure. This angle is called a glancing angle or grazing angle. It is used in such applications as X-ray spectroscopy and atom optics, where the significant reflection usually can be achieved only at small values of the grazing angle. Ridged mirrors are designed for reflection of atoms coming at a grazing angle. This angle is usually measured in milliradians. A surface normal, or just normal to a flat surface is a three-dimensional vector which is perpendicular to that surface. ... X-ray spectroscopy is a gathering name for several spectroscopic techniques for determining the electronic structure of materials by using x-ray excitation. ... Atom optics (or atomic optics) is the section of Physics which deal with beams of neutral atoms, as a special case of a particle beams. ... // In atomic physics, a ridged mirror (or ridged atomic mirror, or Fresnel diffraction mirror) is a kind of atomic mirror, designed for the specular reflection of neutral particles (atoms) coming at the grazing incidence angle, characterised in the following: in order to reduce the mean attraction of particles to the... The radian is a unit of plane angle. ...

## Aviation

Another common usage is in aviation, where it refers to the angle between the wing's chord and the longitudinal axis of an aircraft (a fixed value). Fig. 2 shows a side view of part of an aeroplane. The wing (dotted blue line) makes an angle a with the fuselage (solid blue line). The wings are typically mounted at a small positive angle of incidence, to allow the fuselage to be "flat" to the airflow in normal cruising flight. Angles of incidence of about 6° are common on most general aviation designs. Image File history File links Angle_of_incidence_(wing). ... Image File history File links Angle_of_incidence_(wing). ... Aviation refers to flying using aircraft, machines designed by humans for atmospheric flight. ... Cross section of an airfoil showing chord In reference to aircraft, chord refers to the distance between the front and back of a wing, measured in the direction of the normal airflow. ... General aviation (abbr. ...

Another term for angle of incidence in this context is rigging angle. It should not be confused with the angle of attack, which is the angle the wing chord presents to the airflow in flight. Note that some ambiguity in this terminology exists, as some engineering texts that focus solely on the study of airfoils and their medium may use either term when referring to angle of attack. The use of the term "angle of incidence" to refer to the angle of attack occurs chiefly in British usage. In this diagram, the black arrow represents the direction of the wind. ... Results from FactBites:

 Angle of incidence - Wikipedia, the free encyclopedia (261 words) Angles of incidence of about 6° are common on most general aviation designs. It should not be confused with the angle of attack, which is the angle the wing chord presents to the airflow in flight. An angle of incidence is the angle between a beam incident on a surface and the line perpendicular to the surface at the point of incidence, called the normal.
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