Physics - Geometrical Optics Question with Solution | TestHub

Using the formula $\begin{array}{rl}\frac{1}{v}-\frac{1}{u}& =\frac{1}{f}\\ \frac{1}{v}-\frac{1}{-30}& =\frac{1}{20}\\ v& =60\mathrm{cm}\end{array}$If the image is formed at the centre of curvature of the mirror, the coincidence is possible. Then the rays refracting through the lens will fall normally on the convex mirror and retrace their path of form the image at $O$. Hence, the distance between lens and mirror will be $60-10=50\mathrm{cm}$.