To describe the reflection of light, we will use the following terminology. The incoming light ray is called the incident ray. The light ray moving away from the surface is the reflected ray. The most important characteristic of these rays is their angles in relation to the reflecting surface. These angles are measured with respect to the normal of the surface. Thenormal is an imaginary line perpendicular to the surface. The angle of incidence, θi is measured between the incident ray and the surface normal. The angle of reflection, θr is measured between the reflected ray and the surface normal.
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