# Angle Of Incidence

## Definition - What does Angle Of Incidence mean?

Angle Of Incidence is the first angle at which the ray enters a surface. It is the measure of deviation of something from a straight on such as the angle where the horizontal tail or wing of airplane is installed on fuselage. In optics, it is defined as the angle between the incident ray on any surface and line which is perpendicular to surface at a point of incidence. This ray can be created by any wave – acoustic, X-ray, optical or so on.

## Petropedia explains Angle Of Incidence

The ray which approaches or enters a surface is called incident ray and ray that reflects back and leaves the surface is called reflected ray. At the point where the ray approaches the surface a perpendicular line or ray known as normal divides the angle between reflected ray and incident ray. That angle between incident ray and normal ray is the Angle Of Incidence. According to the law of reflection, the Angle Of Incidence is equivalent to the angle of reflection, which is the angle between reflected ray and normal ray.