A certain far-sighted person cannot see objects closer to the eye than $ 100 \mathrm{~cm} $. The power of lens which will enable him to read at a distance of $ 25 \mathrm{~cm} $ will be

Question

A certain far-sighted person cannot see objects closer to the eye than $ 100 \mathrm{~cm} $. The power of lens which will enable him to read at a distance of $ 25 \mathrm{~cm} $ will be, $ 3 $ dioptre, $ 1 $ dioptre, $ 4 $ dioptre, $ 2 $ dioptre

MARKS App · Accepted Answer

For the required lens, Image distance v = - 100 cm Object distance u = - 25 cm Using the lens equation: 1 v - 1 u = 1 f 1 - 100 - 1 - 25 = 1 f ⇒ f = 100 3 = 33 . 33 cm Power of the lens: 1 f = 1 0 . 33 = 3 D

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