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A convex lens of focal length 20 cm is p...

A convex lens of focal length 20 cm is placed in contact with a concave lens of focal length 12.5 cm in such a way that they have the same principal axis. Find the power of the combination .

Text Solution

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`P=P_1+P_2.`
Here,` P_1=1/(20 cm)=+1/(0.20 m)=5 D` and `P_2=- 1/(125 cm) = - 1/(0.125 m) =-8 D`.
So, the power of the combination is `P_1+P_2=-3D`.
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