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Weight of a person is 800 N. If he runs ...

Weight of a person is 800 N. If he runs 4 m on a vertical ladder in 2s then he needs a power of

A

`-5.2D`

B

`-4.54D`

C

`+5.2D`

D

`+4.7D`

Text Solution

Verified by Experts

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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