Question

A 5 cm tall object is placed perpendicular to the principle axis of a convex lens of focal length 12 cm. The distance of the object from the lens is 8 cm. Using the lens formula, find the position, size and nature of the image formed.

Answer 1

u = −8 cm

f = 12 cm

h = 5 cm

Now lens formula is

`1/v-1/u=1/f`

Putting Values

`1/v=1/12+1/-8`

`=1/12-1/8`

`=(2-3)/24=-1/24=>v=-24`cm

Thus, image is formed 24 cm on the left of convex lens i.e. on the side of the object.

Now magnification is `m =v/u=h^'/h`

`(-24)/(-8)=h^'/5`

h′ = 15 cm (Positive)

The height of the image is 15 cm which is 3 times larger than the height of object.

Thus, we can say image is virtual, enlarged and erect.