In the law of reflection, the angle of incidence is equal to which angle?

• A. Angle of reflection
• B. Angle of transmission
• C. Angle of deviation
• D. Angle of refraction

Answer: (A)

When light hits a smooth surface and reflects, the directions before and after contact are tied to the normal to the surface at the point of incidence. The angle between the incoming ray and that normal is equal to the angle between the reflected ray and the same normal. That equality is the law of reflection in action. The angle of incidence is measured from the normal, and the angle of reflection is the corresponding angle on the other side of the normal. Since the light stays in the same medium during reflection, there’s no refraction or transmission involved, which is why those terms don’t apply here. The angle of deviation, meanwhile, is the angle between the incoming and outgoing rays themselves, not the angle relative to the normal.