A 4 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 24 cm. The distance of the object from the lens is 16 cm. Find the position, size and nature of the image formed, using the lens formula.

Solution:

For convex lens

f=+24cm,u=−16cm

Using lens formula

(1/f)=(1/v)−(1/u)

(1/24)=(1/v)−(1/−16)

=(1/v)+(1/16)

(1/v)=(1/24)−(1/16)

=(2−3)/48

=−1/48

v=−48cm

h₁ = 4 cm

So magnification, m = h₂/h₁ = v/u

h₂= (v/u) x h₁

= (-48/-16) x 4

= 12 cm

Position of image is formed at a distance of 48 cm on the same side of the object. It is indicated by the negative sign

The size of image is three times the size of object i.e., 12 cm.

The image is virtual and erect.