Question

The near point of a person suffering from hypermetropia is 75 cm . calculate the focal length and power of the lens required to enable him to read newspaper which is kept at 25 cm from his eye​

Answer 1

Answer:

1st focal length:

$\frac{1}{f} = \frac{1}{u} + \frac{1}{v} \\ or. \: \frac{1}{f} = \frac{1}{75} + \frac{1}{25} = \frac{1 + 3}{75} = \frac{4}{75} \\ f = \frac{75}{4} = 18.75cm$

2nd power of the lens:

$p = \frac{1}{f} = \frac{1}{18.75} = 0.053d$

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