Four combinations of two thin lenses are given in List-I. The radius of curvature of all curved surfaces is r and the refractive index of all the lenses is 1.5. Match lens combinations in List-I with their focal length in List-II. Image
List 1
List 2
(1) 2r
(2) r/2
(3) - r
(4) r
Options

Question

Four combinations of two thin lenses are given in List-I. The radius of curvature of all curved surfaces is r and the refractive index of all the lenses is 1.5. Match lens combinations in List-I with their focal length in List-II. Image

List 1

List 2

(1) 2r
(2) r/2
(3) - r
(4) r

Options

G1 Physics · Accepted Answer

For each shown combination, calculate the power of each thin element using the lens-maker relation P = (μ - 1)(1/R₁ - 1/R₂), with μ = 1.5, and add the powers of elements in contact. The four shown combinations give P→r/2 (item 2), Q→r (item 4), R→ - r (item 3), and S→2r (item 1). Thus P-2, Q-4, R-3, S-1, option B.