## At A Glance

### Spherical Mirrors

Check us out at http://www.tutorvista.com 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 are illustrated in The most commonly occurring examples of concave mirrors are shaving mirrors and makeup mirrors. As is well-known, these types of mirrors magnify objects placed close to them. The most commonly occurring examples of convex mirrors are the passenger-side wing mirrors of cars. These type of mirrors have wider fields of view than equivalent flat mirrors, but objects which appear in them generally look smaller (and, therefore, farther away) than they actually are. Let us now introduce a few key concepts which are needed to study image formation by a concave spherical mirror. As illustrated in the normal to the centre of the mirror is called the principal axis. The mirror is assumed to be rotationally symmetric about this axis. Hence, we can represent a three-dimensional mirror in a two-dimensional diagram, without loss of generality. The point at which the principal axis touches the surface of the mirror is called the vertex. The point , on the principal axis, which is equidistant from all points on the reflecting surface of the mirror is called the centre of curvature. The distance along the principal axis from point to point is called the radius of curvature of the mirror, and is denoted . It is found experimentally that rays striking a concave mirror parallel to its principal axis, and not too far away from this axis, are reflected by the mirror such that they all pass through the same point on the principal axis. This point, which is lies between the centre of curvature and the vertex, is called the focal point, or focus, of the mirror. The distance along the principal axis from the focus to the vertex is called the focal length of the mirror, and is denoted f
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