From which point are the angles of incidence and reflection measured?

The angles of incidence and reflection are both measured from the normal line, which is an imaginary line that is perpendicular to the surface at the point where the light ray strikes the surface. When light hits a reflective surface, the angle of incidence is the angle between the incoming light ray and the normal line. Similarly, the angle of reflection is the angle between the outgoing light ray and the normal line. This definition is crucial in understanding the law of reflection, which states that the angle of incidence is equal to the angle of reflection. This concept ensures accurate measurements and predictions about how light behaves when reflecting off surfaces. Other references, such as the light source or the surface itself, do not provide a consistent or standardized basis for measuring these angles.