at a plane surface. Let Q be a luminouspoint, q the focus of re-flected rays, E an eye inany position. Then Q willbe seen by means of a smallcone of rays having Q forits vertex, and the apertureof the eye for its base;and the actual course of the pencil from Q will be as in thefigure. 79. If… … 80. As another example let us take the case of a lumi- THE EYE. 521 nous point between two mirrors, as in Art. 29, and trace thepencil by means of which the luminous point will be seen afterany number of reflexions by an eye situated any where in theplane passing through the point and perpendicular…
![An illustration from Cours d'architecture enseigné dans l'Academie royale d'architecture : premiere[-cinquième] partie ... (1675)](https://img.insideoutlibrary.com/img/200/ia-coursdarchitectu00blon-232-101.webp)
