Find the spot on the mirrorSourced
Where should light hit a curved mirror?
Leonardo tried a device.
Alhazen's problem asks where light must strike a spherical mirror to travel between two points. The 11th-century scholar Ibn al-Haytham treated it in general form. According to researcher Roberto Marcolongo, Leonardo da Vinci devised a mechanical tool for it.
When drawing was hard,
a mechanism offered another route.
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Reviewed: 2026-10-01