Some Important Terms Used in the reflection of Light
Let us consider the reflection of light by a plane mirror as shown in the diagram.
INCIDENT RAY
Any ray of light that strikes the reflecting surface is called the incident ray. In the figure above. ‘AO’ is the incident ray.
POINT OF INCIDENCE
The point of incidence is that point at which light is incident on the reflecting surface. That is, the point at which the incident ray falls on the reflecting surface.
In the figure above, ‘O’ is the point of incidence.
NORMAL
The perpendicular drawn to the reflecting surface at the point of incidence is called normal. In the figure above, ‘ON’ is the normal.
REFLECTED RAY
The ray of light which is turned back after reflection into the same medium in which the incident light is travelling is called reflected ray.
In the figure above, OB is the reflected ray.
ANGLE OF INCIDENCE
The angle of incidence is the angle made by the incident ray with the normal at the point of incidence.
Or
The angle between the incident ray and the normal to the surface is called angle of incidence.
In the figure above, the angle ÐAON is the angle of incidence.
ANGLE OF REFLECTION
The angle of reflection is the angle made by the reflected ray with the normal at the point of incidence.
Or
The angle between the reflected ray and normal to the surface is called angle of reflection. In the figure above, the angle ÐBON is the angle of reflection.