Physics - Geometrical Optics Question with Solution | TestHub

$\mathrm{f}=20 \mathrm{cm}$, $\mathrm{m}=4$ $\therefore \mathrm{m}=\frac{\mathrm{v}}{\mathrm{u}}=4\Rightarrow \mathrm{v}=4\mathrm{u}$ Using the formula, we have $\begin{array}{l}\frac{1}{\mathrm{f}}=\frac{1}{\mathrm{v}}-\frac{1}{\mathrm{u}}\end{array}$ $\frac{1}{20}=\frac{1}{\mathrm{u}}-\frac{1}{\mathrm{u}}\Rightarrow \frac{1}{20}=\frac{1-4}{4\mathrm{u}}$$\Rightarrow \frac{1}{20}=\frac{-3}{4\mathrm{u}}\Rightarrow 4\mathrm{u}=-60$$\therefore \mathrm{u}=-15$Putting the value of $\mathrm{u}$, we get $\mathrm{v}=4\mathrm{u}=4\times (-15)=-60$  $\therefore$  Object distance $\mathrm{u}=15 \mathrm{cm}$, image distance $\mathrm{v}=60 \mathrm{cm}$