Reflection of Light by Plane Mirror:
Def: The phenomenon of bouncing back of light rays in the same medium when they strike/incident on a smooth flat surface of an object.
Explanation: For mirrors, more than 95% of light may be reflected. Let us understand the concept of reflection from the given side diagram. Reflection of light is like bouncing back of a rubber ball after hitting a wall or any other hard surface.
From the side diagram, we can see that a ray PO is striking the polished surface (MM') of the mirror at point O and then bouncing back in the same medium through a ray OQ.
Here PO - Incident Ray, OQ - Reflected Ray, O - Point of Incidence, i - Angle of Incidence, r - Angle of Reflection, Normal - Perpendicular line dividing PO and OQ.
The above concept shows that the reflection of a light ray obeys the following two laws known as Laws of Reflection.
Laws of Reflection:
The following are the TWO laws of reflection, they are:
1. Angle of Incidence (<i) is equal to angle of reflection (<r) i.e., <i=<r
2. The incident ray, reflected ray and the normal lies in a same plane.
Note: The above two laws of reflection are valid for all types of surfaces including spherical surfaces.
4 Characteristics of plane mirror:
1. The image formed by a plane mirror is virtual, erect and of the same size as that of the object.
2. In a plane mirror, object distance and image distance are same.
3. The size of image and object are equal.
4. The image formed is laterally inverted.
Uses of Plane Mirror:
1. Plane mirror is used as seeing/looking mirror in dressing table to see our own image.
2. It is used in the construction or making of periscope.
3. It is used in automobiles for various uses.
4. It is used in torch light.
5. It is used as shaving mirror.
