Select the correct statements :

            I) The focal length of the mirror is f and distance of the objects from the focus is u, the

            magnification of the mirror is f/u

            II)$\text{Magnification\hspace{0.17em}}=\frac{\text{size\hspace{0.17em}of\hspace{0.17em}image}}{\text{sizeofobject}}\text{.}$

            III) The mirrors used in search lights are parabolic and not concave spherical

            IV) In a concave spherical mirror the image formed is always virtual