Which statement about the normal line is true?

• A. It lies parallel to the surface.
• B. It bisects the angle between the incident and reflected rays.
• C. It is drawn perpendicular to the reflecting surface at the point of incidence.
• D. It is always coincident with the incident ray.

Answer: (C)

The normal line is the line perpendicular to the reflecting surface at the point where the light hits. This perpendicular line provides the reference for measuring angles of incidence and reflection—the incoming and outgoing rays form equal angles with this line. Because it is defined by being perpendicular to the surface, it cannot lie parallel to the surface and it is not the same line as the incoming ray. The idea that it bisects the angle between the incident and reflected rays comes from those equal angles with the normal, but the defining property you use to identify the normal is its perpendicularity to the surface.