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.
Spherical mirrors have coma unless the field stop is at the center of curvature, like in Schmidt Camera (around f/2.5). It is good to know that a paraboloid mirror of long f/ratio (f/10 for example) and an equivalent long focal spherical mirror will have equivalent coma. Therefore an additional optical element in the form of a corrector lens must be used to manage this aberration.