Physics - Geometrical Optics Question with Solution | TestHub

The focal length of a thin biconvex lens is $20\mathrm{cm}$. When an object is moved from a distance of $25\mathrm{cm}$ in front of it to $50\mathrm{cm}$, the magnification of its image changes from $m_{25}$ to $m_{50}$. The ratio $\frac{m_{25}}{m_{50}}$ is