Question

3. The magnification of an object placed infront of convex lens
of focal length_20 cm is ta to obtain a magnification of
the object will have to be moved at a distance
equal to — ?
-2​

Answer 1

Answer:

It is given that a convex lens of focal length

f=+20cm

m=+2

∵m=

u

v

v=2u..........(1)

Using lens formula

v

1

−

u

1

=

f

1

2u

1

−

u

1

=

20

1

u=−10cm

Hence, object is placed at a distance of 10 cm in front of lens.