Activity: Demonstrating that the incident ray, the reflected ray, and the normal at the point of incidence lie in the same plane

To visually illustrate that the incident ray, the reflected ray, and the normal at the point of incidence lie in the same plane, we can conduct a simple experiment using a flat mirror and a light source. The steps for the activity are as follows:

Materials required:
- Flat mirror
- Light source (e.g., flashlight, laser pointer)
- Ruler or protractor (optional)

Procedure:
1. Set up the flat mirror on a stable surface, ensuring that it is perpendicular to the ground. The mirror should be clean and free from any smudges or dirt.
2. Position the light source such that it emits a narrow beam of light towards the mirror. The light should hit the mirror at an angle.
3. Turn off any surrounding lights to enhance visibility.
4. Observe the incident ray, reflected ray, and the normal at the point of incidence on the mirror's surface.

Explanation:
The incident ray is the incoming ray of light that strikes the mirror's surface. The reflected ray is the ray that bounces off the mirror after striking it. The normal at the point of incidence is an imaginary line perpendicular to the mirror's surface at the point where the incident ray strikes.

When the light beam hits the mirror, it follows the law of reflection, which states that the angle of incidence is equal to the angle of reflection. This means that the angle between the incident ray and the normal is equal to the angle between the reflected ray and the normal.

By observing the behavior of the incident and reflected rays, we can conclude that they both lie in the same plane as the normal. This is because the incident ray, the reflected ray, and the normal all intersect at the same point, which is the point of incidence on the mirror's surface. Since three non-collinear points determine a plane, we can confirm that the incident ray, reflected ray, and the normal at the point of incidence all lie in the same plane.

Note:
- Using a ruler or protractor, one can measure the angles of incidence and reflection to verify that they are equal, further reinforcing the concept of the incident and reflected rays lying in the same plane as the normal.