Q5. 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.
Place a plane mirror on the table. Take a piece of paper and make a small hole in it. Ensure that the light in the room is dim. Hold the sheet normal to the table. Take another piece of paper and place it on the table in contact with the mirror. Draw a normal from the mirror on the paper kept on the table Now, light a torch on the mirror through the small hole such that the ray of light falls on the normal at the bottom of the mirror. When the ray from this hole is incident on the mirror, it gets reflected in a certain direction. You can easily observe the incident ray, reflected ray and the normal to the mirror at the point of incidence on the sheet placed on the table. This shows that the incident ray, the reflected ray, and the normal to the surface at the point of incidence all lie in the same plane.
Material required:- white sheet of paper, a drawing board, drawing pins, a comb.
Procedure:
(i) A white sheet of paper on a drawing board is fixed.
(ii) A strip of plane mirror is taken and placed in the path of light ray.
(iii) The ray of light will be reflected.
(iv) Angle of incidence and angle of reflection on the sheet of paper is drawn.
(v) The incident and reflected rays along the paper is observed.
(vi) Now the sheet of paper is bent a little at the position of the reflected ray.
(vii) Keeping the incident ray and the normal in the plane of the drawing board, the reflected ray is tried be seen now.
Observation:
The incidence ray, reflected ray and normal lie in same plane.