Angle of incidence

Fig.1

Fig.2

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). Note: 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).

Another common usage is in aviation, where it refers to the angle between the wing's chord and the fuselage. Fig.2 shows a side view of part of an aeroplane. The wing (dotted blue line) makes an angle α withe 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. AoI's of about 6° are common on most general aviation designs.

See Also

Optics