Question

An object 5 cm high is placed 40 cm in front of a converging lens of focal length 20 cm
Find the position, size and nature of image.​

Answer 1

$\large{\bf{\gray{\underline{\underline{\orange{Given:}}}}}}$

Distance of object = 40cm

Focal length = 20cm

Type of lens : converging (convex)

Height of object = 5cm

$\large{\bf{\gray{\underline{\underline{\green{To\:Find:}}}}}}$

We have to find position, size and nature of image.

$\large{\bf{\gray{\underline{\underline{\pink{Solution:}}}}}}$

Focal length of convex lens is taken positive.

⛥ Position of image :-

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

$:\implies\tt\:\dfrac{1}{v}=\dfrac{1}{20}+\dfrac{1}{(-40)}$

$:\implies\tt\:\dfrac{1}{v}=\dfrac{4-2}{80}$

$:\implies\boxed{\bf{\blue{v=40\:cm}}}$

⛥ Size of image :

$:\implies\tt\:m=\dfrac{v}{u}=\dfrac{I}{o}$

$:\implies\tt\:\dfrac{40}{(-40)}=\dfrac{I}{5}$

$:\implies\boxed{\bf{\red{I=-5\:cm}}}$

⛥ Nature of image :

• Real
• Inverted
• Equal size