Shown an object and its image formed by a thin lens. Then the nature and focal length of lens is

Options

A. `f=4.8cm` converging lens
B. `f=-4.8 cm ` diverging lens
C. `f=2.18cm` converging lens
D. `f=-2.18cm` diverging lens

Answer

b.

Explanation

`(1)/(v)-(1)/(u)=(1)/(f)`
`v=-3cm,u=-8cm`
`(1)/(-3)-(1)/(-8)=(-8+3)/(24)=(-5)/(24)`
`f=(-24)/(5) cm=-4.8cm` (diverging lens)