Two identical thin plano convex glass lenses refractive

Last updated: 6/1/2023

Two identical thin plano convex glass lenses refractive index 1 5 each having radius of curvature of 20 cm are placed with their convex surfaces in contact at the centre The intervening space is filled with oil of refractive index 1 7 The focal length of the combination is 1 25 cm 3 50 cm 2 50 cm 4 20 cm