Question

A convex lens of focal length 12cm produces an image on a screen 3 times in size than the object what is the distance of the object from the lens?

Answer 1

given

focal length = 12cm

u =?

v=minus 3

according to mirror formula

1/v +1/u =1/f

on putting the values

1/minus 3 +1/u =1/12

1/u = minus 4 + 1/12 = minus 3/12 = minus 1/4

1/u = minus 1/4 u= minus 4

hope it hlpz