angle of reflection

The angle of reflection is the angle between a reflected light ray and the normal at the point it bounces off a mirror.

• The first law of reflection states that the angle of reflection is always exactly equal to the angle of incidence — a rule confirmed by measuring both angles carefully across many trials with different incoming beam directions.
• This equality holds for every kind of mirror, not just flat ones — plane, concave, and convex mirrors alike all obey it at each individual point where light strikes them.
• It's the combination of many equal angle-of-incidence/angle-of-reflection pairs across a curved surface that makes a whole beam of parallel rays converge or diverge, even though each single ray is just obeying the same simple rule.
• Knowing the angle of reflection lets you predict exactly where a reflected ray will travel next — the basis for designing everything from bathroom mirrors to satellite dishes.