In optics, angle of incidence can be defined as the angle between a ray incident on a surface and the line perpendicular to the surface at the point of incidence
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The ray of light that hits the polished surface is called the incident ray. The ray that gets reflected away is called the reflected ray. The point at which the light hits the surface is called the point of incidence. If a line is drawn perpendicular to that point, it is called the normal.