Angle of incidence - Light, Colour, Vision

The angle of incidence measures the angle at which incoming light strikes a surface.

The angle of incidence is measured between a ray of incoming light and an imaginary line called the normal.
When light is travelling towards something it is said to be incident to that surface or object.
Incident light may have travelled from the Sun or an artificial source or may have already been reflected off another surface such as a mirror.
When incident light strikes a surface or object it may undergo absorption, reflection, refraction, transmission or any combination of these optical effects.

If one line is normal to another, then it is at right angles.
In geometry, a normal (or the normal) refers to a line drawn perpendicular to and intersecting another line, plane or surface.
In the field of optics, the normal is a line drawn on a ray diagram perpendicular to (at 90⁰ to), the boundary between two media.
If the boundary between two media is curved then the normal is drawn at a tangent to the boundary.

Each of the diagrams below can be viewed on its own page with a full explanation.

$Refraction Towards the Normal$

$Refraction Away from the Normal$

$Reflection & Refraction - Flat Boundary$

$Reflection & Refraction - Curved Boundary$

The angle of incidence measures the angle at which incoming light strikes a surface.

The angle of incidence is measured between a ray of incoming light and an imaginary line called the normal.
In optics, the normal is a line drawn on a ray diagram perpendicular to, so at a right angle to (90⁰), the boundary between two media.
If the boundary between the media is curved, then the normal is drawn at a tangent to the boundary.