Earlier still or dark water collected in a vessel was considered or used as mirrors by ancient people. Then as days passed obsidian mirrors came into existence followed by metal coated glass mirrors this led to discovery of metal coated spherical or parabolic mirrors. A spherical mirror is a mirror which has the shape of a piece cut out of a spherical surface. There are two types of spherical mirrors: concave, and convex. These mirrors are also known as parabolic mirrors discovered in mid9th century Ibn al haytham and Ibn sahl.parabolic mirrors were described in classical antiquity written by mathematician-Diocles . In addition to these researches Ptolemy also carried out experiments with curved polished iron mirrors and discussed about convex spherical and concave spherical mirrors in his book optics.
In spite of these researchers finding the focal length of spherical mirror was a tough task but finally Ibn al-Hay tham got a breakthrough by finding out the focal length of curved surfaces using the laws of reflection.he stated that “All the reflected rays of a mirror converge or diverge and meet at a point known as focus and the distance between focus and pole of mirror is known as focal point of mirror.’’Also many scientists came to a conclusion that spherical mirrors can be divided into concave and convex mirrors. Spherical mirrors Concave mirrors Convex mirrors The invention of concave and convex mirrors led to many changes and have become a part of our life.
