Question

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

Answer 1

Hint: The point of this activity must be to prove that the normal incident ray and reflected ray lie in the same plane. We can also choose to prove that the point of incidence on the mirror is in plane with the incident and reflected ray.

Complete step by step answer:
Requirements: Two cardboard sheets (or boxes) of identical size, a laser pointer, two identical rulers, a marker and a small mirror.
Procedure:
1. Place the two sheets parallel to each other in a firm manner.
2. Now take two rulers and place on the top of the two sheets facing each other.
3. On one cardboard, fix a small plane mirror while on the other, fix the pointer by making a hole. The pointer should make an angle with the mirror but should point towards it.
4. With the help of the ruler, mark the position of the pointer.
5. Switch the pointer on and note the position of the point on the mirror where you observe the point.
6. Then note the reflected point from it on the second cardboard sheet.
7. If you place another firm sheet joining the three concerned points, you will notice that the sheet will be able to connect the three points without leaving any point out.
See the figure for reference.

Thus, we can prove that the incident ray, reflected ray and the normal lie in the same plane.

Note:
Use a laser of low power if you look at a high power laser it might cause a permanent burn in your eye. Pleasure has been used here because if you use another light source then it might not be able to reproduce the reflected light as a point.