Explanation: Height of the object $\mathit{h}=4\mathrm{cm}$
Object distance, $\mathit{u}=-30\mathrm{cm}$
Focal length, $\mathit{f}=10\mathrm{cm}$ (Diverging mirror)
Using mirror formula,
$1∕\mathit{v}+1∕\mathit{u}=1∕\mathit{f}$
$\mathit{u}∕\mathit{v}=\mathit{u}∕\mathit{f}-1$
$=\left(-30∕10\right)-1$
$=4$
Magnification, $\mathrm{m}=$ image height/Object height $=-\left(\mathit{v}∕\mathit{u}\right)$
$=1∕4$
Image height $=\mathit{h}∕4=4∕4=1\mathrm{cm}$