Alhazen's problem
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Alhazen's problem is a mathematical problem in optics concerning reflection in a spherical mirror. It asks for the point in the mirror where one given point reflects to another. The special case of a
Spherical mirror from the Alaska–Yukon–Pacific Exposition (1909)
The caustic generated by a point source of light (bright point, top) within a circular mirror (light red). This illustration extends each light ray past the mirror to a complete line. For one given point at the light source, Alhazen's problem has two solutions for a second given point on the dark side of the caustic and four solutions on the light side of the caustic.
In geometry, straightedge-and-compass construction – also known as ruler-and-compass construction, Euclidean construction, or classical construction – is the construction of lengths, angles, and other
Alhazen's problem
…11th-century Arab mathematician Alhazen (Hasan Ibn al-Haytham), who formulated it more generally and presented a solution in his Book of Optics. It has no straightedge and compass construction; instead, al-Haytham and others including Christiaan Huygens found solutions involving the intersection of conic sections. According to Roberto Marcolongo…
Straightedge and compass
A compass