When light interacts with a mirror, the angle at which it reflects from the mirror's surface is determined by the law of reflection. According to this law, the angle of incidence (the angle between the incoming light ray and the normal to the mirror's surface) is equal to the angle of reflection (the angle between the reflected light ray and the normal to the mirror's surface). This relationship can be expressed mathematically as follows:
θᵢ = θᵣ
Where: θᵢ = Angle of incidence θᵣ = Angle of reflection
The normal is an imaginary line perpendicular to the surface of the mirror at the point of incidence, which serves as a reference direction. When light strikes the mirror's surface, it interacts with the atoms or molecules of the mirror material. These interactions cause the light to bounce back or reflect off the surface.
The reason light reflects from a mirror at an angle from the normal is due to the conservation of energy and the wave nature of light. When light encounters a boundary between two different media (in this case, air or another medium and the mirror), it undergoes a change in speed and direction. This change is known as refraction. In the case of a mirror, however, the light reflects rather than refracts because the mirror is highly reflective and does not allow light to pass through easily.
The law of reflection ensures that the incident light and the reflected light maintain a consistent relationship in terms of their angles with respect to the mirror's surface normal. The angle of incidence and the angle of reflection are equal but measured on opposite sides of the normal.
This predictable behavior of light reflection is what allows mirrors to produce clear and accurate reflections, making them valuable in various applications such as optics, imaging systems, and everyday objects like mirrors in our households.