In the figure shown here, what is the equivalent focal length of the combination of lenses? (Assume all layers

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In the figure shown here, what is the equivalent focal length of the combination of lenses? (Assume all layers are thin, R = 20 cm , outer lenses μ=1.6 , inner lens μ=1.5 ) ![image](https://pub-7faa453bd1ec4bf0a04cc031c6f058de.r2.dev/images/1af6dd34-4f36-4971-9c50-a03c5552d6ce.png)

Accepted Answer

Power P = 1/f = (μ - 1)≤ft(1/R_1 - 1/R_2) .Outer plano-concave lenses ( P_1 and P_3 ): μ=1.6, R_1 = ∞, R_2 = 20 . P_1 = P_3 = (1.6 - 1)≤ft(1/∞ - 1/20) = -0.6/20 = -0.03 cm^-1 .Inner bi-convex lens ( P_2 ): μ=1.5, R_1 = 20, R_2 = -20 . P_2 = (1.5 - 1)≤ft(1/20 - ≤ft(-1/20)) = 0.5 × 2/20 = 0.05 cm^-1 .Equivalent Power P_eq = P_1 + P_2 + P_3 : P_eq = -0.03 + 0.05 - 0.03 = -0.01 cm^-1 F_eq = 1/P_eq = -100 cm . ![image](https://pub-7faa453bd1ec4bf0a04cc031c6f058de.r2.dev/images/7ff88c82-9bd2-4a08-90b6

In the figure shown here, what is the equivalent focal length of the combination of lenses? (Assume all layers are thin, $R = 20 cm$ , outer lenses $μ = 1.6$ , inner lens $μ = 1.5$ )

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In the figure shown here, what is the equivalent focal length of the combination of lenses? (Assume all layers are thin, R=20cm, outer lenses μ=1.6, inner lens μ=1.5)