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A person with spectacles of power 3m ^(...

A person with spectacles of power `3m ^(-1)` can see distinctly the letters of newspaper placed at a distance of 25 cm from the eye. At what distance should the newspaper be kept to be able to read it without spectacles?

Text Solution

Verified by Experts

The power of the lens of the spectacles `=3 m ^(-1)`. If f be the focal length of the lens, then,
`3=(100)/f or, f=(100)/3 cm `
Again u =-25 cm and f=`(100)/3 cm`.
So from the equation `1/v-1/u=1/f` we have ,
`1/v+1/(25)=3/(100) or, 1/v=3/(100)-1/(25) or, v=-100 cm `
So to read the newspaper without spectacles the person will have to place it at a distance of 100 cm from the eye.
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