How is Focal Length related to Radius of Curvature? Mirror formula Definition : The equation relating the object distance (u) the image distance (v) and the mirror focal length (f) is called the mirror formula.Assumptions made :The mirror has a small aperture. The object lies close to principal axis of the mirror. The incident rays make small angles with … [Read more...] about How is Focal Length related to Radius of Curvature?