What is called focus of mirror?

Focus of a Mirror

The focus of a mirror, specifically a concave mirror, is defined as the point where light rays parallel to the principal axis converge after reflection. In the case of a convex mirror, the focus refers to the point from which the light rays appear to diverge after reflecting off the mirror surface.

Concave Mirror Focus

In a concave mirror, rays of light that are parallel to the principal axis reflect and converge at a single point known as the focal point. The distance from the mirror to the focal point is called the focal length. This physical focus point exists in front of the mirror.

Convex Mirror Focus

For a convex mirror, parallel light rays reflect and spread out. The rays seem to come from a virtual focus located behind the mirror. Since the light does not actually pass through this point, the focal point of a convex mirror is virtual and cannot be projected onto a screen. The distance of this point from the mirror, following the path the light would have taken were it not reflected, is referred to as the focal length.

The focal length (f), for a spherical mirror, can be calculated using the mirror equation, which relates the object distance (p), the image distance (q), and the focal length:

1/f = 1/p + 1/q