Distances measured in mirror problems must follow a definite rule. Answer the questions that follow with reference to this rule.
a. (i) State the sign convention used for measuring object distance u, image distance v and focal length f for spherical mirrors.
b. (ii) Using this convention, explain why the focal length of a concave mirror is negative while that of a convex mirror is positive.
c. (iii) A student calculates the magnification of a mirror to be m=−2. Explain what the negative sign of m tells about the nature and orientation of the image.