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Two thin lines of powers -4D and 2D are ...

Two thin lines of powers -4D and 2D are placed in contact coaxially. Find the focal length of the combination.

Text Solution

Verified by Experts

Net power, `P = P_1 + P_2`
or `P = -4D + 2D = -2D`
Focal length, f ` = 1/P = (1)/(-2) = -50 cm`
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