Laws of Reflection
1. Angle of Incidence = Angle of Reflection: This is the fundamental law of reflection. The angle between the incident ray and the normal (a line perpendicular to the mirror surface) is equal to the angle between the reflected ray and the normal.
2. Incident Ray, Reflected Ray, and Normal lie in the same plane: All three lines are in the same plane.
Applying it to Normal Incidence
When a ray of light falls normally on a plane mirror, the angle of incidence is 0 degrees. Since the angle of incidence equals the angle of reflection, the angle of reflection is also 0 degrees.
This means that the reflected ray coincides with the incident ray, making it appear as if the light simply passes through the mirror without changing direction. In reality, the light is reflected back along the same path.
Visualizing it
Imagine a straight line perpendicular to a mirror. If you shine a light beam along that line, it hits the mirror directly (at 0 degrees). Because the angle of reflection is also 0 degrees, the reflected light travels back along the same line.
In summary: The laws of reflection dictate that the angle of incidence and reflection are equal. When a ray of light falls normally on a mirror, the angles are both 0 degrees, resulting in the reflected ray retracing the path of the incident ray.
