Source edition
Euclid. Euclidis Opera Omnia, Volume 7. Menge, Heinrich; Heiberg, J.L, editors. Leipzig: Teubner, 1895.
Source data
Open Greek and Latin · CC BY-SA 4.0
Cloned and adapted by Humanitext, with ongoing edits.
Summary
This work is a geometrical treatise on the science of vision and light, focusing on the laws of reflection in plane, convex, and concave mirrors. Written in a structured format of mathematical propositions, the text begins by establishing the fundamental law of reflection, stating that the angle of incidence equals the angle of reflection. In the opening sections, the author defines the pathways of reflected visual rays and explains how images appear erect, inverted, or reversed. The middle section provides rigorous geometric proofs regarding the characteristics of images—such as their size, distance, and orientation—across different types of mirrors. The discussion then progresses to more complex phenomena, including multiple reflections using arrays of mirrors and the specific conditions of visibility when an eye is placed at various positions relative to a concave mirror. Finally, the work concludes with practical applications, demonstrating how to construct composite mirrors that produce multiple images and geometrically proving how a concave mirror can concentrate sunlight to ignite a fire.