Question

A concave mirror produces a real image of half the size of an object placed at 60 cm infront of it. Where should the object be placed to obtain a virtual image of double the size of the object?

Answer 1

intial object distance u = -60cm(real object_)

magnification m $=-\frac{1}{2}$

from $m=\frac{-f}{u-f}$

from above $f=-20cm$

let the object distance be $u^{\prime }$

magnification $m^{\prime }=2\times$ image of virtual real object

$m=\frac{-f}{u^{\prime }-f}$

$2=\frac{20}{u^{\prime }+20}⟹u^{\prime }=10cm$

hence the object should be at a distance of 10cm infront of the mirror