Question

A convex lens of focal length 10cm is placed at a distance of 12 cms from a wall how for from the lens should an object be placed so as to form its real image on the wall

Answer 1

We can say that v=12cm

1/f=1/v -1/u

1/u=1/v- 1/f

1/u=1/12-1/10

1/u=5-6/60

u=-60cm

So the object should be placed at 60cm from the lens to obtain a real image on the wall