Which line is the normal line in reflection?

Which line is the normal line in reflection?

• A. A line drawn along the surface of the mirror.
• B. A line drawn perpendicular to the incident ray.
• C. A line drawn perpendicular to the reflecting surface at the point of incidence.
• D. A line that lies halfway between the incident and reflected rays.

Answer: (C)

The normal line is the line that is perpendicular to the reflecting surface at the point where the light ray meets the surface. It provides the reference for measuring the angles of incidence and reflection, which are equal when light reflects. The surface itself runs along the tangent to the boundary, not perpendicular to it, so a line along the surface isn’t the normal. A line perpendicular to the incident ray isn’t the defining reference for reflection, and the line halfway between the incident and reflected rays would be the bisector of the angle between them, not the normal. So the line that is perpendicular to the reflecting surface at the point of incidence is the normal.

The normal line is the line that is perpendicular to the reflecting surface at the point where the light ray meets the surface. It provides the reference for measuring the angles of incidence and reflection, which are equal when light reflects. The surface itself runs along the tangent to the boundary, not perpendicular to it, so a line along the surface isn’t the normal. A line perpendicular to the incident ray isn’t the defining reference for reflection, and the line halfway between the incident and reflected rays would be the bisector of the angle between them, not the normal. So the line that is perpendicular to the reflecting surface at the point of incidence is the normal.