Parabolic Mirrors
A parabolic mirror is a specially shaped object designed to capture energy and focus it to a single point or distributing energy from a single point. There are alos parabolic dishes and parabolic reflectors.
The surface of a parabolic mirror is known as a paraboloid of revolution. This is a type of elliptical paraboloid that is rotated around its axis and may also be referred to as a circular paraboloid. By using a parabolic mirror, reflecting telescopes correct some of the aberrations which exist in refracting telescopes.
There are also drawback, one of which is a problem called coma which causes any objects viewed through the telescope which are not at the centre of the field of vision to look slightly wedge-shaped. The further outside the field they are, the more distorted they appear.
The mirrors are usually made of a low expansion glass, similar to Pyrex glass. The mirrors are kept as fine as possible to reduce distortion in the image. The processes used to produce extremely high-end parabolic mirrors can take months and cost thousands of dollars.
Parabolic mirrors can be used to create solar furnaces. The flame used for the Olympic torch is lit using a large parabolic mirror. This parabolic mirror collects ambient sunlight and focuses it to an intensity sufficient to ignite the torch material.
