A mirror whose polished, reflecting surface is a part ofa hollow sphere of glass is called a spherical mirror. For a spherical mirror, one of the two curved surfaces is coated with a thin layer of silver followed by a coating of red lead oxide paint. Thus, one side of the spherical mirror is made opaque, and the other side acts as a reflecting syrface. The opaque side of a mirror is shown shaded.
Depending upon the nature of the reflecting surface of the mirror, the spherical mirrors may be classified as -
The first mirror used by the ancient people were dark,still water collected in a primitive vessle.
The earliest manufacturing spherical mirrors were polished obsidian stones.The obsidian are naturly formed volcanic glass.