Two thin lenses with powers +5 D and -3 D in contact. Equivalent power:
A-2 D
B+2 D (= +5 + (-3))
C+15 D
D+8 D
Answer & Solution
Correct answer: B. +2 D (= +5 + (-3))
In contact: P_eq = P₁ + P₂ = 5 - 3 = 2 D. Equivalent focal length f = 1/2 = 0.5 m = 50 cm (convex). Sign rules apply.
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