Question

An object is placed $25cm$ from a convex lens whose focal length is $10cm$. The image distance is ...............
($50cm,16.66cm,6.66cm,10cm$)

Answer 1

Given:

Focal length, $f=10cm$

Object distance, $u=-25cm$

From lens formula,

$\frac{1}{f}=\frac{1}{v}-\frac{1}{u}$

$\frac{1}{10}=\frac{1}{v}-\frac{1}{-25}$

$\frac{1}{10}=\frac{1}{v}+\frac{1}{25}$

$\frac{1}{10}=\frac{25+v}{25v}$

$25v=250+10v$

$25v-10v=250$

$15v=250$

Therefore, the image distance, $v=\frac{250}{15}=16.66cm$