Question

(i) Size of image of an object formed by a mirror having a focal length of 20 cm is observed to be reduced to ()rd of its
size. At what distance, the object has been placed from the mirror? What is the nature of the image and the mirror?(ii) An
object is placed at a distance of 50cm form a concave lens of focal length 20 cm. Find the nature and position of
the image.​

Answer 1

Answer:

1)Using magnification formula,

m=−

u

v

=

3

1

⇒v=−

3

u

From mirror formula,

v

1

+

u

1

=

f

1

From above two equations,

−u

3

+

−u

1

=

20

1

u=−80 cm

So, the object is placed at a distance of 80cm in front of the mirror.