Question

Where should an object be placed in front of concave mirror of focal length 20 cm so as to produce a 2times magnified real image ?

Answer 1

$$\begin{gathered} DearStudent, \\ Sinceitis2timesmagnified,m=-2 \\ so-\frac{v}{u}=-2----\left(1\right) \\ similarly\frac{1}{v}+\frac{1}{u}=\frac{1}{f} \\ so\frac{1}{v}+\frac{1}{u}=\frac{1}{-20} \\ \frac{-v}{v}+\frac{-v}{u}=\frac{-v}{-20}(multiplythroughoutbt-v) \\ -1-2=\frac{-v}{-20} \\ v=-60 \\ nowfrom\left(1\right) \\ u=-30 \\ Sotheobjectmustbeplaced30cmfromthemirrorthatisbetweenfand2f \\ Regards \end{gathered}$$