Question

A lens of focal length 12cm forms an erect image three times the size of the object. The distance between the object and the image is
A)8cm. B)16cm. C)24cm. D)36cm

Answer 1

Relation for image size

image size = Focal Length X Object size / Lens-to-object distance

form the prob focal length =12 cm

object size = m

image size = 3m

form the above formula

Lens-to-object distance= Focal Length X Object size/ Image Size

= 12 X m /3m= 4 cm

but

distance between object to image = distance object to lense

+ distance lense to image

distance between object and lense is nothing but the focal length of the lense that is 12 cm

so, distance between object to image = 12 + 4 = 16 cm