Reflection in a plane mirror and how two people see each other's eyes
Rays, refraction from rare to dense, and touching the friend's eye on the mirror
This leaf gathers studies of vision, reflection and refraction drawn as eyes with rays. Leonardo notes that a ray passing from the rare to the dense bends its straightness on entering, and that no one sees another person's likeness in a mirror in the place where it truly falls unless the eye lies on the line of the images. In a lettered diagram (mirror n o, your friend's eye b, your eye d) he shows that the visual lines cross at m, so that whoever touches m touches the open eye of the other person; a marginal note adds that every particle of an object occupies the whole facing surface of the mirror. Much of the sheet is faint and further untranscribed text is present.
On this page
Where two people's visual lines cross on a mirror
With n o the mirror, b your friend's eye and d your own, your friend's eye appears to you at a and yours appears to him at c; the visual lines intersect at m, so that whoever touches m touches the open eye of the other person.
A ray bends passing from the rare to the dense
One eye sees a ray leave the light and go downward; another sees the light mirrored at b between two rays. Leonardo explains that a ray going from the rare medium to the dense bends its straight path on entering the dense.
Likeness on the mirror falls at equal angles
No man will see the likeness of another upon the mirror in the proper place where it is reflected, because each object falls on the mirror at equal angles; unless the observing eye lies on the line of the images it will not see it where it falls, and entering those lines it covers the other man and sets itself over his likeness.