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A person wear normal spectacles in which...

A person wear normal spectacles in which the distance of glasses and eyes is approximately 2 cm. then power required is -5D if the wears contact lens, then the requires power is

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Text Solution

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The correct Answer is:
B
Contact lens is more effective, so its required power is less

For glasses
`(1)/(v)-(1)/(u)=(1)/(f)implies(1)/(-x)-(1)/(oo)=(1)/(f)`
`f=-x" "cm=-(x)/(100)`
power`=(1)/(f)=-(100)/(x)=-5impliesx=20cm`
if he used lens.

`v=-oo,u=-22cm`
`(1)/(v)-(1)/(u)=(1)/(f)implies(1)/(-oo)=(1)/(f)`
`f=-22,p'=-(100)/(22)D=-4.54D`
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