Definition: The word 'arclight' was a term for light coming out of an angle or ray, typically used in astronomy and optics to describe visible light from stars. A reference point is called the "light source." The word originally meant light falling on a flat surface, but it became more general over time. A light ray passing through a specific point (the "light point") makes an "arclight angle" with the normal of that point. This angle can be calculated using trigonometry.
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