The angle of incidence equals the angle of reflection describes which lighting law?

• A. Law of reflection
• B. Law of refraction
• C. Law of diffusion
• D. Law of absorption

Answer: (A)

The main idea here is how light behaves when it hits a reflective surface. When a light ray strikes a smooth, shiny surface, the angle it makes with the perpendicular to that surface (the normal) on the way in is the same as the angle it makes with the normal on the way out. Both rays lie in the same plane—the incident ray, the reflected ray, and the normal all share that plane. This is the law of reflection.

In lighting design, this helps predict where light will go after hitting walls, mirrors, or other reflective surfaces, guiding where to place fixtures and how to aim them for the desired brightness and glare control.

The other listed principles describe different phenomena: refraction involves bending of light as it moves into a different medium (like air to glass) and is described by Snell’s law; diffusion is the scattered spread of light from rough surfaces; absorption is about how much light energy a surface takes in rather than reflects.