# Spherical mirrors

## Construction of ray diagrams

Construction of ray diagrams Since a point on an image can be located by the point of intersection of two reflected rays, we have to consider which are the most convenient rays to use for this purpose. Remembering that, by geometry, the normal to a curved surface at any point is the radius of curvature at that point, …

## The focal length of a spherical mirror is half its radius of curvature

The focal length of a spherical mirror is half its radius of curvature In Fig. 22.3 AB is an incident ray parallel and close to the principal axis PC of a concave mirror. By definition, the reflected ray passes through the principal focus F. Since by geometry, the radius CB is normal to the mirror surface at B, …

## Mirrors of large aperture

Mirrors of large aperture The remarks in the previous paragraph apply only to mirrors which are small in size or aperture compared with their radii of curvature. This is not the case with a hemispherical mirror, for instead of producing a point focus from a parallel beam, the reflected rays intersect to form a surface called a …

## Principal focus

Principal focus When a parallel beam of light falls on a plane mirror it is reflected as a parallel beam; but in the case of a concave mirror the rays in a parallel beam are all reflected so as to converge to a point called a focus. If the incident rays are parallel to the principal axis …

## Spherical mirrors

Spherical mirrors In this chapter we shall study the way in which images are formed by curved mirrors. The kind we use are generally made by silvering a piece of glass which would form part of the shell of a hollow sphere. Silvering the glass on the outside gives a concave or converging mirror, while silvering on the …