Describe an activity to show that the incident ray, the reflected ray and the normal at the point of incidence lie in the same plane.

Spread a sheet of paper on horizontal table and place a mirror vertically on it. Take second sheet of paper and make a small hole in it 1 cm from the bottom. Place it vertically on the table on the shining part of the mirror. Turn off the lights of the room. Light the torch on opposite side to the vertical sheet of paper. A single ray of light will pass through the hole. Use scale and find the height of the ray of light at different positions. Positions must include points on incident ray, points on reflected ray and plane of incidence(here mirror). Record the heights. You will find that all points on the ray of the light is at a height 1 cm. Since all points are equidistant from horizontal plane, they all lie on the same plane.