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A long sighted man cannot see clear objects that are less than 120cm away what is the type of focal length of lens required to make him read a book 30cm away ? |
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Answer» Answer: He NEEDS a convex lens of focal length of 40CM...... u=30cm, v=-120cm 1/f=1/u + 1/v 1/f=1/30 - 1/120 1/f=4-1/120 1/f=3/120 3f=120 f=120/3 .: f = 40 cm... |
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