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.

Take a sheet of stiff paper or a chart paper. Let the sheet project a little beyond the edge of the table. Cut the projecting portion of the sheet in the middle. Look at the reflected ray. Make sure that the reflected ray extends to the projected portion of the paper. Bend that part of the projected portion on which the reflected ray falls.

When the whole sheet of paper is spread on the table, it represents one plane. The incident ray, the normal at the point of incidence and the reflected ray are all in this plane.

When we bend the paper we create a plane different from the plane in which the incident ray and the normal lie. Then we do not see the reflected ray.

Hence, the above activity indicates that the incident ray, the normal at the point of incidence and the reflected ray all lie in the same plane.