Question

A lens of focal length 12cm produces an erect image three times the size of object. What is the distance between object and image?​

Answer 1

Magnification , m=

u

v

3=

u

v

⇒v=3u

Lens formula :

v

1

−

u

1

=

f

1

3u

1

−

u

1

=

12

1

3u

−2

=

12

1

⇒u=−8cm

v=3×−8=−24cm

Distance between object and image =u−v=−8−(−24)=−8+24=16cm