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Which has greater power a convex lens of focal length 10 cm or 20 CM |
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Answer» Power = 1 / Focal length ( in m ) Focal Length 1 = 10 cm = 0.01 m Power = 1 / 0.01 m = 100 / 1 = 100 D Focal Length 2 = 20 cm = 0.02 m Power = 1 / 0.02 = 100 / 2 = 50 D Hence Focal length 1 has greater power than Focal length 2. Alternate method : We know that Power is INVERSELY PROPORTIONAL to Focal length. Hence more focal length implies LESS power. Hence Focal length of 10 cm has greater power than 20 cm. |
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