Reflection
The bouncing back of a light ray or wave when it strikes a boundary surface between two different media without entering the second medium.
Governing formula
θ_i = θ_r
SI unit
Degrees (°)
In depth
According to the Law of Reflection, the angle of incidence equals the angle of reflection, and the incident ray, reflected ray, and surface normal all lie in the same plane. Can be specular (mirror-like smooth surface) or diffuse (rough surface).
Examples in the real world
Light reflecting off a flat glass mirror forming a crisp virtual image, or sunlight scattering diffusely off a painted wall.