Physics - Geometrical Optics Question with Solution | TestHub

Given, square wire of side $=2\mathrm{cm}$, $u=-20\mathrm{cm},f=-10\mathrm{cm}$, Area of second wire $=$ ? $\begin{array}{rlrl}& \therefore & \frac{1}{v}+\frac{1}{u}& =\frac{1}{f}\\ & \Rightarrow & \frac{1}{v}+\frac{1}{(-20)}& =\frac{1}{-10}\Rightarrow \frac{1}{v}=-\frac{1}{10}+\frac{1}{20}\\ & \Rightarrow & v& =-20\mathrm{cm}\end{array}$ We know that, $m=-\frac{v}{u}=\frac{-(-20)}{-20}=-1$ $\because \frac{\text{ Area of image }}{\text{ Area of object }}=m^2\Rightarrow \frac{A_i}{A_0}=(-1{)}^2$ $\frac{A_i}{2\times 2}=1$ $\Rightarrow A_i=4{\mathrm{cm}}^2$