An object is 12 cm in front of a converging lens with focal length 4 cm. Where is the image?

The image distance v= - 3cm

This implies that the image is virtual and I front of the principal focus

Explanation:

This problem bothers on curved mirrors

Given data

Object distance =12cm

Focal length =-4cm

(the negative sign as indicated is used because the converging mirror has a virtual focus)

Let the image distance =v

Applying

1/v +1/u= 1/f

1/v+1/12=1/-4

1/v=1/(-4)-1/12

= LCM 24

= - 6-2/24

1/v = - 8/24

1/v= -1/3

v= - 3cm

This implies that the image is virtual and I front of the principal focus.

increase masses, decrease separation