A spherical mirror produces an image at a 48 cm distance in front of it when an object is positioned 12 cm from its pole. If the object size is 5mm, calculate the size of the image formed.

The size of the object is given as $5 \mathrm{mm}$. 
Let us find out the magnification so that the size of the image can be found. The magnification of the image is the ratio of the height of the image to the height of the object or the negative ratio of image distance to object distance. 

The image distance is given as$\mathrm{ }48\mathrm{cm}$ the object distance is given as$\mathrm{ }12\mathrm{cm}$.
 $\mathrm{ }\mathrm{M}=\frac{{\mathrm{h}}_{\mathrm{i}}}{{\mathrm{h}}_{\mathrm{o}}}=\frac{-\mathrm{v}}{\mathrm{u}}$
$\Rightarrow \mathrm{M} =-\frac{-48}{-12}$
 $\mathrm{M}=-\mathrm{ }4$
So, to obtain the size of the image, we must multiply the size of the object with magnification. $\mathrm{Height} \mathrm{of} \mathrm{the} \mathrm{image} =\mathrm{ }-4\mathrm{ }\times 5$
$=-\mathrm{ }20 \mathrm{mm}.$

The negative sign denotes that the image is real and inverted.