Question

A lens forms a virtual, diminished image of an object placed at `2 m` from it. The size of image is half of the object. Which one of the following statements is correct regarding the nature and focal length of the lens ?
A. Concave `|f|=1m`
B. Convex, `|f|=1`
C. Concave,`|f|=2m`
D. Convex, `|f|=2m`

Answer 1

Correct Answer - C
`m=(f)/(f+u),(1)/(2)=(f)/(f-2)`
or `2f=f-2` or `f=-2 metre`
`|f|=2 metre`
Since the image is virtual as well as diminished therefore the lens is concave.