Question
To Find focal length of a convex lens in laboratory, Manoj fixed it on a stand and kept it on a mark of 15.3 cm an optical bench. To get a clear image of a distant tree, he adjusted a screen and finally got clear image when screen was placed at 32.5 cm. Focal length of the lens is :
(a) 32.5 cm (b) 17.2 cm (c) 34.4 cm (d) 47.8 cm