Following Figure shows three arrangements of lenses. The radii of curvature of all the curved surfaces are same. The ratio of the equivalent focal length of combination P, Q and R is :
1
1 ∶ 1 ∶ 1
2
1 ∶ 1 ∶ -1
3
2 ∶ 1 ∶ 1
4
1 : ∞ : 2
Following Figure shows three arrangements of lenses. The radii of curvature of all the curved surfaces are same. The ratio of the equivalent focal length of combination P, Q and R is :