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Mirror is the name given to any surface or laminated glass silvered by the later, or brushed metal, so that it reflected objects. By extension is called mirror to any surface that produces reflection of objects, eg. : Water surface.

Elements of spherical mirrors:

curvature Center: The center of the field to cap belongs.

bending radius: The radius of the sphere it belongs to the mirror.

Vertex Mirror: The pole of the spherical cap to which the mirror.

Main Shaft: The line through the apex and the center of curvature

Secondary axis: Each of the lines passing through the center of curvature.

opening (or angle) of the mirror: The angle formed by the secondary axes passing through the edge of the mirror.

In the spherical mirrors are checked the same laws of reflection in plane mirrors. In fact, it is considered that the point of incidence of the beam belongs to the plane tangent to the spherical mirror, at that point.

The path of the rays and outbreaks:

In concave spherical mirrors, it holds that:

• All the major axis parallel rays are reflected through the focus (located on the main shaft).

• Any beam passing through the principal focus is reflected parallel to the main shaft.

• Every ray that passes through the center of curvature, are reflected on himself. This is easily explained in geometric form, as if passing through the center of curvature, is a radio and all radio is perpendicular to the tangent to the circle at the point where this radius intersects the circumference.

• It can be shown geometrically that the main focus of a spherical mirror is the midpoint of the radius of curvature. Given the relationship between this and the focal length, we can also say-and prove-that the focal length is equal to half the radius of curvature.

far we have spoken of concave spherical mirrors, let us turn now to the convex :

These also comply with the law of reflection known and analyzed, but we must make the clarification that: the main focus of a spherical convex mirror is virtual, therefore, the focal length of a convex mirror is negative.

can easily verify that the path of the rays in the cases of convex spherical mirrors, is similar to the path in the concave mirrors, but ... as the focus is virtual, we say:

• Any beam parallel to the main axis in a convex mirror is reflected so that its extension passes through the focus.

• Each ray incident on a convex mirror tends to go through the focus is reflected parallel to the main shaft.

• Any incident beam toward the center of the mirror, it reflects on itself.

The picture that emerges in a spherical convex mirror is virtual, in the same direction and less than the object reflected.