If we want to obtain a virtual and magnified image of an object by using a concave mirror of focal length 18 cm, where should the object be placed?…

Object should be placed between F and P / At less than 18cm distance from the mirror. \[\text { Mirror formula }=\frac{1}{v}+\frac{1}{u}=\frac{1}{f} \] \[\begin{aligned} \frac{1}{-2 u}+\frac{1}{u} & =\frac{1}{-18 c m} \\ \therefore \frac{1}{2 u} & =\frac{1}{-18 \mathrm{~cm}} \end{aligned} \] \[\mathrm{U}=-9 \mathrm{~cm} \]