Spherical mirror

A spherical mirror is a spherically polished reflector made of glass, ceramic, metal or similar materials. As a ceramic or glass mirror, it is relatively easy to manufacture - see mirror grinding - and in the form of the concave mirror it is used , for example, for small mirror telescopes or for shaving mirrors . As a reducing convex mirror , it can be found as a traffic mirror or as a rear-view mirror for cars.

As geometrical optics shows, a spherical mirror generally has severe aberrations . They only disappear for reflections from the center of the sphere , where the light rays return. The focal point for rays incident in parallel - i.e. plane waves from infinity - is, however, about half the radius of the sphere.

If plane waves are to be reproduced exactly, the reflector must not be spherically ground, but in the form of a paraboloid . However, its production is much more complicated. Such parabolic mirrors are absolutely necessary for astronomical mirror telescopes from a certain size (at least for the so-called eight - inch model ) or light intensity (as with good headlights ).

See also:

• spherical aberration
• Metal mirror
• Condenser