Perform Activity again. This time use a sheet of stiff paper or a chart paper. Let the sheet project a little beyond the edge of Table Fig. 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. Can you still see the reflected ray? Bring the paperback to the original position. Can you see the reflected ray again? What do you infer?
Incident ray, reflected ray and the normal at the point of incidence lie in the same plane.
Yes, the reflected ray of light is seen on the sheet. It is concluded that the entire sheet fixed on the drawing board represents a plane. The incident, reflected ray and the normal lie in the plane of paper.