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Correct option is A)

By lens makers' formula,

So focal length of 2 identical plano-convex lens is given by, $f1 =241 =(1.5−1)(∞1 −−R1 )+(1.5−1)(R1 −∞1 )⟹R=24cm$

The total focal length of the lens combination can be given as,

$f_{t}1 =(1.5−1)(∞1 −−R1 )+(1.6−1)(−R1 −R1 )+(1.5−1)(R1 −∞1 )$

$⟹f_{t}1 =R−0.2 ⟹f_{t}=−120cm$

Option A is correct

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