Question

A 8 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 30 cm. The distance of the object from the lens is 60 cm. Its position & size of image is-

Answer 1

Given:

A 8 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 30 cm. The distance of the object from the lens is 60 cm.

To find:

Position and size of image ?

Calculation:

Applying Len's Formula:

$\therefore \: \dfrac{1}{f} = \dfrac{1}{v} - \dfrac{1}{u}$

$\implies\: \dfrac{1}{30} = \dfrac{1}{v} - \dfrac{1}{( - 60)}$

$\implies\: \dfrac{1}{30} = \dfrac{1}{v} + \dfrac{1}{60}$

$\implies\: \dfrac{1}{v} = \dfrac{1}{30} - \dfrac{1}{60}$

$\implies\: \dfrac{1}{v} = \dfrac{1}{60}$

$\implies\: v = 60 \: cm$

So, image is formed at 60 cm from lens.

$\therefore \: \dfrac{ h_{i}}{h_{o}} = \dfrac{v}{u}$

$\implies \: \dfrac{ h_{i}}{8} = \dfrac{60}{ - 60}$

$\implies \: h_{i} = - 8 \: cm$

So, image is same size that of object and is inverted.