All Topics  
Angle of incidence

 

 
   Email Print
   Bookmark   Link
 

 

Angle of incidence
 
 
  Topics Angle of incidence Topic Home

Angle of incidence is a measure of deviation of something from "straight on", for example:

eometric optics, the angle of incidence is the angle between a ray incident on a surface and the line perpendicular to the surface at the point of incidence, called the normal
Surface normal

A surface normal, or simply normal, to a Flatness is a vector which is perpendicular to that surface. A normal to a non-flat surface at a Point P on the surface is a vector perpendicular to the Tangent space to that surface at P....
.






Discussion
Ask a question about 'Angle of incidence'
Start a new discussion about 'Angle of incidence'
Answer questions from other users
Full Discussion Forum



Encyclopedia


Angle of Incidence
Angle of incidence is a measure of deviation of something from "straight on", for example:
  • in the approach of a ray
    Ray (optics)

    In optics, a ray is an idealized narrow beam of light. Rays are used to model the propagation of light through an optical system, by dividing the real light field up into discrete rays that can be computationally propagated through the system by the techniques of Ray tracing ....
     to a surface, or
  • the angle at which the wing
    Wing

    A wing is a surface used to produce Lift for flight through the Earth's atmosphere or another gaseous or fluid medium. The wing shape is usually an airfoil....
     or horizontal tail
    Stabilizer (aircraft)

    For aircraft, the horizontal stabilizer or tailplane is a fixed or adjustable surface from which an elevator may be hinged. In some aircraft models , the entire horizontal stabilizer rotates and functions as an elevator....
     of an airplane is installed on the fuselage
    Fuselage

    The fuselage is an aircraft's main body section that holds crew and passengers or cargo. In single-engine aircraft it will usually contain an engine, although in some amphibious aircraft the single engine is mounted on a hardpoint attached to the fuselage which in turn is used as a floating Hull ....
    , measured relative to the axis of the fuselage.


Optics

In geometric optics, the angle of incidence is the angle between a ray incident on a surface and the line perpendicular to the surface at the point of incidence, called the normal
Surface normal

A surface normal, or simply normal, to a Flatness is a vector which is perpendicular to that surface. A normal to a non-flat surface at a Point P on the surface is a vector perpendicular to the Tangent space to that surface at P....
. The ray can be formed by any wave: optical, acoustic, microwave
Microwave

Microwaves are electromagnetic radiation with wavelengths ranging from 1 mm to 1 m, or frequency between 0.3 hertz and 300 GHz....
, X-ray
X-ray

X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 10 to 0.01 nanometers, corresponding to frequency in the range 30 Hertz to 30 Hertz and energies in the range 120 Electron volt to 120 keV....
 and so on. In the figure above, the red line representing a ray makes an angle ? 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.

Grazing angle

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 that between the beam and the surface normal
Surface normal

A surface normal, or simply normal, to a Flatness is a vector which is perpendicular to that surface. A normal to a non-flat surface at a Point P on the surface is a vector perpendicular to the Tangent space to that surface at P....
, in other words 90° minus the angle of incidence. This angle is called a glancing angle or grazing angle. Incidence at small grazing angle is called "grazing incidence".

Grazing incidence is used in X-ray spectroscopy
X-ray spectroscopy

X-ray spectroscopy is a gathering name for several Spectroscopy techniques for determining the electronic structure of materials by using x-ray excitation....
 and atom optics
Atom optics

Atom optics is the area of physics which deals with beams of cold, slowly moving neutral atoms, as a special case of a particle beam.Like an optical beam, the atomic beam may exhibit diffraction and interference, and can be focused with...
, where significant reflection can be achieved only at small values of the grazing angle. Ridged mirror
Ridged mirror

In atomic physics, a ridged mirror is a kind of atomic mirror, designed for the specular reflection of neutral particles coming at the grazing incidence angle, characterised in the following: in order to reduce the mean attraction of particles to the surface and increase the reflectivity, this surface has narrow ridges....
s are designed for reflection of atoms coming at small grazing angle. This angle is usually measured in milliradians.

Aviation

In aviation
Aviation

File:Norwegian military Bell 412SP helicopters.jpgAviation refers to activities involving man-made flying devices , including the people, organizations, and regulatory bodies involved with them....
, angle of incidence is the angle between the wing's chord
Chord (aircraft)

In reference to aircraft, chord refers to the distance between the leading edge and trailing edge of a wing, horizontal stabilizer or vertical stabilizer, measured in the direction of the normal airflow....
 and the longitudinal axis of an aircraft (a fixed value). The figure to the right shows a side view of part of an aeroplane. The wing (dotted blue line) makes an angle a with the longitudinal axis (roll axis) of the aircraft (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
General aviation

General aviation is one of two categories of civil aviation. It refers to all flights other than military aviation and scheduled air transport flights, both private aviation and commercial aviation....
 designs.

Another term for angle of incidence in this context is rigging angle. It should not be confused with the angle of attack
Angle of attack

Angle of attack is a term used in aerodynamics to describe the angle between the chord of an airfoil and the vector representing the relative motion between the airfoil and the air....
, which is the angle the wing chord presents to the airflow in flight. Note that some ambiguity
Ambiguity

Ambiguity is the property of being ambiguous, where a word, term, notation, sign, symbol, phrase, Sentence , or any other form used for communication, is called ambiguous if it can be interpreted in more than one way....
 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.

See also

  • Effect of sun angle on climate
    Effect of sun angle on climate

    The amount of heat energy received at any location on the globe is a direct effect of sun angle of climate, as the Angle of incidence at which sunlight strikes the earth varies by location, time of day, and season due to the earth's orbit around the sun and the earth's revolution around its tilted axis....
  • Reflection (physics)
    Reflection (physics)

    Reflection is the change in direction of a wavefront at an wiktionary:interface between two differentmedium so that the wavefront returns into the medium from which it originated....
  • Refraction
    Refraction

    Refraction is the change in direction of a wave due to a change in its speed. This is most commonly observed when a wave passes from one optical medium to another....
  • Season
    Season

    A season is one of the major divisions of the year, generally based on yearly periodic changes in weather.Seasons result from the yearly revolution of the Earth around the Sun and the Axial tilt....
  • Snell's law
    Snell's law

    In optics and physics, Snell's law , is a mathematical formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves, passing through a boundary between two different isotropic medium , such as water and glass....
  • Total internal reflection
    Total internal reflection

    Total internal reflection is an optical phenomenon that occurs when a ray of light strikes a medium boundary at an angle larger than the critical angle with respect to the normal to the surface....