Question

An object of height 4 cm is placed in front of a concave lens of power -2.5 D at a distance of 40 cm .magnification produced by the concave lens will be

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.