Angle of Incidence at a Spherical Mirror
Rays from a luminous point reflected to the eye; a large circle labelled a–i with an inner arc K–S
A large circle is crossed by a fan of straight rays, with a smaller circle at the lower centre labelled 'spherical mirror'. The heading states that the construction seeks the angle of incidence, while the outer circumference is lettered a through i (marked as eye positions) together with a luminous point t, and an inner arc carries the letters K L m n o p q r S. The drawing works out geometrically how a ray from the luminous source strikes the spherical mirror and is directed to the observing eye.
On this page
Seeking the angle of incidence
The heading announces that the figure is built to find the angle of incidence of a reflected ray. Rays fan out from a source toward the mirror and on to the eye, so that the geometry of reflection can be measured.
The spherical mirror at the centre
The small circle at the lower centre of the figure is labelled the spherical mirror, the reflecting surface on which the rays fall. The luminous point t and the several eye positions are ranged around the outer circumference.
Circumferences lettered for the reflection construction
The outer circumference is divided and labelled a, b, c, d as eye positions and e, f, g, h, i, with t marked as the luminous point; the inner arc carries the letters K L m n o p q r S. These labelled points fix the rays and angles of the construction.