Question

An object is placed at a distance at a distance of $10cm$ in front of a concave lens of focal length $10cm$. Find the linear magnification of the lens?

• A. 1
• B. $\frac{1}{2}$
• C. $\frac{1}{3}$
• D. $\frac{1}{4}$

Answer 1

The correct option is B

$\frac{1}{2}$

Given:

$u=-10cm$

$f=-10cm$

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

$=\frac{1}{v}=\frac{1}{u}+\frac{1}{f}=\frac{1}{-10}-\frac{1}{10}=\frac{-2}{10}=-\frac{1}{5}$

$v=-5cm$

Thus the image is formed at a distance $5cm$ in front of the lens.

Linear magnification, $m=\frac{v}{u}=\frac{-5cm}{-10cm}=\frac{1}{2}$

$m=\frac{1}{2}$