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A lens has a power of -2.5 D. Its focal length is:
A+40 cm
B-40 cm
C-25 cm
D+2.5 cm
Answer & Solution
Correct answer: B. -40 cm
f = 1/P = 1/(-2.5) m = -0.4 m, which is -40 cm, a diverging lens.
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