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Islamic Scientific Heritage@IslamicSH_ · Sep 19, 2026

Why is Ibn Sahl left out of history? The Muslim genius who pioneered Snell's Law long before it was recognized. Ibn…

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Summary

Ibn Sahl, a 10th-century Muslim mathematician from Baghdad, discovered the law of refraction (Snell's Law) centuries before Snell and designed anaclastic lenses that focus light without geometric aberrations, yet remains largely omitted from mainstream history.

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  1. #1

    Why is Ibn Sahl left out of history? The Muslim genius who pioneered Snell's Law long before it was recognized. Ibn Sahl (d. 1000), was a Muslim mathematician and physicist, who flourished in Baghdad. He was the first to discover the law of refraction (Snell's law). Ibn Sahl uses this law to derive lens shapes that focus light with no geometric aberrations, known as anaclastic lenses. 🧵[THREAD]

  2. #2

    2) Ibn Sahl is the first Muslim scholar known to have studied Ptolemy's Optics. Ibn Sahl dealt with parabolic mirrors, ellipsoidal mirrors, biconvex lenses, and techniques for drawing hyperbolic arcs. Ibn Sahl designed convex lenses that focus light rays that are parallel, which can cause an object to burn at a specific distance.

  3. #3
    Islamic Scientific Heritage@IslamicSH_ · Sep 19, 2026

    @jimalkhalili explains how Ibn Sahl actually discovered Snell’s Law, 650 years before Willebrord Snellius.