Harry is reading an online summary of the law of reflection. The site states that after light hits a mirror, the angle of reflection is the angle between the reflected ray and the normal, which is the surface of the mirror.

The normal is an imaginary line drawn perpendicular (at 90°) to the mirror’s surface at the point where the light hits. The angle of reflection is measured between the reflected ray and this normal, not between the two rays or the incoming ray and the normal. Therefore, the correct choice is “The normal is a line perpendicular to the surface of the mirror.”

AI-written and checked against the verified answer.