In the law of reflection, which statement is true about the relationship between the angle of incidence and the angle of reflection?

• A. They are supplementary
• B. They are unrelated
• C. They are equal
• D. The incidence is twice the reflection

Answer: (C)

The main idea here is that light follows a mirror-like rule: the angle it makes with the normal to the surface at the point of incidence is the same as the angle the reflected ray makes with that same normal, but on the opposite side. In other words, the incoming and outgoing rays are symmetric about the normal, and they stay in the same plane—the plane of incidence. So if the incoming ray hits at 30 degrees to the normal, the reflected ray leaves at 30 degrees to the normal on the other side. This holds for smooth, polished surfaces where reflection is specular; on rough faces, the law still applies to each tiny facet, which is why we get diffuse reflection overall.