Question

a pin is placed in front of a convex lens of focal length 60cm at distance of 15cm. what will be the image distance?​

Answer 1

Given:

A pin is placed in front of a convex lens of focal length 60cm at distance of 15cm.

To find:

Image distance ?

Calculation:

Applying Lens Formula:

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

$\implies\: \dfrac{1}{60} = \dfrac{1}{v} - \dfrac{1}{( - 15)}$

$\implies\: \dfrac{1}{60} = \dfrac{1}{v} + \dfrac{1}{15}$

$\implies\: \dfrac{1}{v} = \dfrac{1}{60} - \dfrac{1}{15}$

$\implies\: \dfrac{1}{v} = \dfrac{1 - 4}{60}$

$\implies\: \dfrac{1}{v} = \dfrac{ - 3}{60}$

$\implies\: \dfrac{1}{v} = \dfrac{ - 1}{20}$

$\implies \: v = - 20 \: cm$

So, image distance is 20 cm in front of lens.