1.

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

Answer»

<P>`-5.2D`
`-4.54D`
`+5.2D`
`+4.7D`

Solution :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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