Question

an object placed 50 cm from a lens produces a virtual image at a distance of 10cm in front of the lens calculate the focal length of the lens and magnification produced

Answer 1

Object distance=-50 cm(applying sign convention)
Since the image distance is lesser than the object distance and a virtual image is formed, it's a concave lens.(v=-10)
We are supposed to use lens formula:-
1/f=1/v-1/u
f is -ve
v is -ve
u is -ve
on simplifying we get
f=25/4 or 6.25 cm.
magnification=-(v/u)
                     =-10/50
=-0.2

Answer 2

Answer:

Explanation:

Object distance=-50 cm(applying sign convention)

Since the image distance is lesser than the object distance and a virtual image is formed, it's a concave lens.(v=-10)

We are supposed to use lens formula:-

1/f=1/v-1/u

f is -ve

v is -ve

u is -ve

on simplifying we get

f=25/4 or 6.25 cm.

magnification=-(v/u)

                    =-10/50

=-0.2