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A short sighted person is wearing specs of power `-3.5 D`. His doctor prescribes a correction of `+ 2.5 D` for his near vision. What is focal length of his distance viewing part and near vision. |
Answer» Correct Answer - `28.5cm` ; `16.7 cm` For distance viewing part , `P_(1) = - 3.5 D` `:. f_(1) = (100)/(P_(1)) = (100)/(-3.5)cm = - 28.5 cm` For near vision part, `P_(1) + P_(2) = P` `P_(2) = P - P_(1) = 2.5 D - (3.5 D) = 6.0 D` `f_(2) = (100)/(P_(2)) = (100)/(6.0) = 16.7 cm` |
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