When an object is moved along the axis is of a lens images three times the size, of the object are obtained when the object is at 16 cm and at 8 cm respectively from the lens. The focal length and nature of the lens are

Options

A. 12 cm concave
B. 4 cm concave
C. 12 cm convex
D. 4 cm convex

Answer

C

Explanation

Since image height is greater than object height lens is convex one image is real and another virtual real image when object is at 16 cm
`u=-16cm,m=-3,m=(v)/(u)implies-3=(v)/(-16)`
`v=48cm`
`(1)/(f)=(1)/(v)-(1)/(u)=(1)/(48)-(1)/(-16)=(1+3)/(48)impliesf=12cm`