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On the ibn al-Haytham / alhasein / alhazen problem.

This paper was enclosed in a letter to Henry Oldenburg dated at Paris [France] on 26 June 1669. The problem attributed to Alhazen (the Latinized name of Ibn al-Haytham (965-1045) is to find a point of reflection on the surface of a spherical mirror in relation to two points, the eye and the visible object.

The diagram and text are printed using a method that Huygens claimed he had invented, making the acid bite all the way through the plate and inking over it, as with a stencil.

Christopher Wren had come up with a similar copying method earlier in 1662.

Subject: Geometry

Published in Philosophical Transactions as 'Excerpta ex epistolis non-nullis, ultrò citróque ab illustrissimis viris, Slusio & Hugenio, ad editorem scriptis, de famigerato albazeni problemate circa punctum reflexionis in speculis cavis aut convexis; & primò quidem ex prima Hugenii'.

Reference number
Earliest possible date
26 June 1669
Physical description
Ink on paper
Page extent
1 page

Creator name

Christiaan Huygens

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Christiaan Huygens, Paper, 'Problema alhasein' [alhasein problem] by Christian Huygens at Paris, 26 June 1669, CLP/1/13, The Royal Society Archives, London,, accessed on 22 June 2024

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  • Classified Papers

    Dates: 1592-1741

    The 'Classified Papers' of the Royal Society are papers from British and international natural philosophers and scholars categorised according to subject areas.

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