Two identical thin planoconvex lenses of refractive index n are silvered, one on the plane side and the other on the convex side. The ratio of their focal lengths is : On-1 2

Two identical thin planoconvex lenses of refractive index n are silvered, one on the plane side and other on the convex side. The ratio of their for lengths is

Two identical thin planoconvex lenses of refractive index n are silvered, one on the plane side and other on the convex side. The ratio of their for lengths is

Two thin plano-convex lenses each of focal length f are placed as shown in the figure . The ratio of their effective focal lengths in the three cases is

Two identical thin planoconvex glass lenses{refractive index 1.5) each having radius of curvature of 20 cm are placed with their convex surface in contact at the centre .The intervening space is filled with oil of refractive index 1.7.The focal length of the combination is.

Two identical thin planoconvex glass lenses (refractive index 1.5) each having radius of curvature of 20 cm are placed with their convex sufaces in contact at the centre. The intervening space is filled with oil of refractive index 1.7 The focal length of the combination is

Two identical thin planoconvex glass lenses (refractive index 1.5) each having radius of curvature of 20cm 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

Two identical thin planoconvex glass lenses (refractive index 1.5) each having radius of curvature of 20cm 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

Two identical thin planoconvex glass lenses (refractive index 1.5) each having radius of curvature of 20cm 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

Two identical thin plano-convex glass lenses (refractive index 1.5) each having radius of curvature of 20 cm are placed with their convex surface in contact at the centre. The intervening space is filled with oil of refractive index 1.7. The focal length of the combination is :