1 Chills and Tingling fingers and Skin symptoms (4 causes) 2  Chills and Tingling fingers and Temperature symptoms (4 causes) 3  Chills and Tingling fingers and Body symptoms (3 causes) 4  Chills and Tingling fingers and Leg symptoms (3 causes)  Chills and Tingling fingers and Limb symptoms (3 causes)
From the geometry of the spherical mirror, note that the focal length is half the radius of curvature: As in the case of lenses, the cartesian sign convention is used here, and that is the origin of the negative sign above. The radius r for a concave mirror is a negative quantity (going left from the surface), and this gives a positive focal length, implying convergence.
The focal length is the distance of the focal point to the lens. Same for a convex lens, except that the focal point is the imaginary point from where light deflected from lens seems to have emerged. The focal point is the point where light converges after it passes through a concave lens. The focal length is the distance of the focal point to the lens. Same for a convex lens, except that the focal point is the imaginary point from where light deflected from lens seems to have emerged.