A convex lens has a focal length of 20 cm. Its power is
Options
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A.
+2 D
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B.
+5 D
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C.
-5 D
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D.
-2 D
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E.
None of the above
Correct Answer (Detailed Explanation is Below)
B.
+5 D
Detailed Explanation
Power P = 1/f in metre. f = 20 cm = 0.20 m, so P = 1/0.20 = +5 D.