Question

A convex lens of focal length 15 cm produces a magnification of + 4 the object is placed at

Answer 1

Here the formulae of magnification must be

Magnification(M)=v/u

As

1/v -1/u = 1/f ...........(1)

Now M=+4(given from the data)

As v/u=4 hence v=4u

Now putting the value of v in the equation above( 1 )

1/4u - 1/u = 1/f

Now f=15cm

(-3/4u)=1/15

u=15*3/4

u=11.25

Answer 2

here is your answer attachment I have send you can find where first is finished and start