A person has been using spectacles of power - | vedclass

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(D) The reading glass is used to correct the near point of the eye to the standard near point of $25 \, cm$.For a reading glass,the object is placed a

Vedclass · Accepted Answer

$50$

Vedclass · Answer

(D) The reading glass is used to correct the near point of the eye to the standard near point of $25 \, cm$.For a reading glass,the object is placed at the standard near point $u = -25 \, cm$,and the image is formed at the person's actual near point $v$.The power of the reading glass is $P = +2.0 \, D$.The focal length $f$ is given by $f = \frac{1}{P} = \frac{1}{2} \, m = 50 \, cm$.Using the lens formula $\frac{1}{v} - \frac{1}{u} = \frac{1}{f}$:$\frac{1}{v} - \frac{1}{-25} = \frac{1}{50}$$\frac{1}{v} + \frac{1}{25} = \frac{1}{50}$$\frac{1}{v} = \frac{1}{50} - \frac{1}{25} = \frac{1-2}{50} = -\frac{1}{50}$$v = -50 \, cm$.The least distance of distinct vision for this person is $50 \, cm$.

$A$ person has been using spectacles of power $-1.0$ diopter for distant vision and a separate reading glass of power $+2.0$ diopters. What is the least distance of distinct vision for this person in $cm$?

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