According to the law of reflection, what is the relationship between the angle of incidence i and the angle of reflection r?

• A. i = r
• B. i > r
• C. i < r
• D. i ≠ r

Answer: (A)

When light reflects off a smooth surface, the path of the incoming ray and the reflected ray are arranged so that each makes the same angle with a line drawn perpendicular to the surface (the normal). This means the angle of incidence equals the angle of reflection. If the light arrives at 30 degrees to the normal, it leaves at 30 degrees to the normal. That’s why i equals r. The other options would imply unequal angles, which doesn’t happen for a smooth mirror under the law of reflection.