Physics - Geometrical Optics Question with Solution | TestHub

In a setup of displacement method experiment, distance between the screen and a light source is 140 cm and the lens used has a small aperture. By moving the lens between the source and the screen, sharp images are obtained on the screen for two different positions of the lens. The ratio of sizes of these two images is 16 : 1 . Find the focal length of the lens (in cm).