Question

A convex lens of focal length 50 cm is placed 20 cm in front of a plane mirror. Light from very far away source falls on the lens. The distance of final image from the mirror is

Answer 1

From lens formula,

f

1

=

v

1

−

u

1

⇒

v

1

=

f

1

+

u

1

=

20

1

−

12

1

=

4

1

(

5

1

−

3

1

)

=−

4

1

(

15

2

)

Image distance for convex lens, v=−30cm

Distance of image formed by lens from mirror =40cm

∴ Final image formed behind the mirror =40cm