A person can not see clearly an object kept at a distance beyond of 100 cm. Find the nature and the power of lens to be used for seeing clearly the object at infinity.

Explanation

For lens u =`-prop` and `u=- 100 cm`
`:. , (1)/(v ) (1)/(v) - (1)/(u) = (1)/(f ) " or " (1)/(v ) = (1)/(f )`
`rArr f = v= - 10 cm `
`:. , ` power of lens `P= (1)/(f ) =- (1)/(1) =- 1 D`