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An equiconvex lens of glass (n = 1.5) has surfaces of radius 30 cm. Its focal length is:
A15 cm
B30 cm
C45 cm
D60 cm
Answer & Solution
Correct answer: B. 30 cm
1/f = 0.5 x (1/30 + 1/30) = 1/30, so f = 30 cm.
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