When a ray of light falls on a polished and shining surface of an object, then it is sent back in the same medium. The process of sending back the light rays after falling on the shining surface of an object is called reflection of light.
Reflection of Light from a Plane Mirror
When a ray of light (AO) falls on a plane mirror at the point O then it gets reflected by the mirror in the direction OB. Now we shall discuss some important terms related with the reflection of light by a mirror.
Incident Ray
The ray of light which falls on the surface of mirror is called incident ray. In figure AO is the incident ray of light.
Point of Incidence
The point at the surface of mirror at which the incident ray falls is called the point of incidence. In figure the point O on the surface of mirror is the point of incident.
Reflected Ray
When the incident ray falls on the surface of a mirror, the mirror sends it back in another direction (in same medium). The ray of light which is sent back by the mirror is called reflected ray.
Normal
Normal may be defined as a line which is perpendicular to the mirror at the point of incidence. In figure line ON is normal to the mirror at point O. the normal is always represented by a dotted line.
Angle of Incidence
The angle of incidence may be defined as the angle which is made by the incident ray with normal at the point of incident. It is denoted by the letter i. In figure the angle AON between the incident ray AO and the normal ON is the angle of incidence.
Angle of Reflection
The angle of reflection may be defined as the angle which is made by the reflected ray with normal at the point of reflection. It is denoted by the letter r. In figure the angle NOB between the reflected ray OB and the normal ON is the angle of incidence.
Test Your Understanding and Answer These Questions:
- Define normal.
- Define reflection of light.
- Define incident ray.
- Define reflected ray.
- Define point of incidence.
- Define angle of incidence.
- Define angle of reflection.