A person is suffering from myopic defect. He is able to see clear objects placed at `15 cm`. What type and of what focal length of lens he should use to see clearly the object placed `60 cm` away ?

Options

A. Concave lens of 20 cm focal length
B. Convex lens of 20 cm focal length
C. Concave lens of 12 cm focal length
D. Convex lens of 12 cm focal length

Answer

A

Explanation

`(1)/(f)=(1)/(v)-(1)/(u)=(1)/(-15)-(1)/(-60)=(-4+1)/(60)`
`f=-20cm`
so cancave lens