Question

1.
A lens of focal length 12cms form an erect image 3 times the size of the
object. Calculate the distance between the object and image.​

Answer 1

Magnification , m = v/u

3 = v / u

v = 3u

Lens formula : 1 / v _ 1 / u = 1 / f

1 / 3u _ 1 / u = 1 / 12

_2 / 3u = 1 / 12

u = _8cm

v = 3 × _8 = _24cm

Distance between object and image = u _ v = _8 _ ( _24 ) = _8 + 24 = 16cm