Islamic Developments in Optics
The Complete History of Science
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The Importance of Ibn Sal in the Development of Science
In his treaties, called simply on burning instruments, Ibn Sal investigates the properties of lenses which could cause burning. He takes a Plano convex hyperbolic lens, that is flat on one side and curved on the other, and uses it to focus light to a point. The effect of this is to concentrate the light rays in the same way as these mirrors. But he wasn't simply satisfied to investigate the practical effect, and was trying to show that such lenses will always cause rays to converge at the opposite side. This is essentially equivalent to what is now known as Snell's Law, and it was not discovered in Europe until the 17th century. Unfortunately it appears like Ibn Sal
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