1. In the case of reflection on mirrors the law of reflection is Angle of incidence ∠i = Angle of reflection ∠r.
2. Proof : by a simple activity.
Take a sheet of blank paper. Draw a line AC on it.
Draw another straight line at right angles to AC.
This line should bisect AC. This line is normal.
Draw two lines from point B on the left side of the normal and two lines on the right side of the normal.
The lines should make angles of 30° and 60° respectively from the normal. Number these lines as 1, 2, 3 and 4 as shown in figure.
- Place the mirror strip vertically on AC. With its reflecting surface facing the normal.
- Take the mirror strip with a slit and let its light ray fall along line 4.
- We find the reflected ray coming along the line 1.
- Note the angle of incidence and angle of reflection.
- Repeat the experiment by sending the light ray along line 3.
- The reflected ray is found to be along line 2.
- Record the observations.
It is clear from the above activity that angle of incidence ∠i = angle of reflection ∠r.
