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Question
Two convex lenses of focal length 30 cm and 10 cm each are kept in contact with each other. Find the power of their combination.
Solution
Given: f1 = 30 cm = 0.30 m, f2 = 10 cm = 0.10 m
To find: Power of combination (P)
Formula: P = `1/"f" = 1/"f"_1 + 1/"f"_2`
Calculation: From formula,
P = `1/"f" = 1/0.30 + 1/0.10 = 1/0.30 + 3/0.30`
`= 4/0.30` = 13.33 D
Power of combination is 13.33 D.
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Solve the following example.
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