Question

A $2cm$ tall object is placed perpendicular to the principal axis of a convex lens of focal length $1cm$. If the object distance is $1.5cm$. Find the magnification.

• A. $2$
• B. $-4.5$
• C. $-2$
• D. $+4.5$

Answer 1

The correct option is C $-2$

Given,

Object distance, $u=-1.5cm$

Focal length, $f=1cm$

Using lens formula,

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

$\frac{1}{1}=\frac{1}{v}-\frac{1}{-1.5}$

$\frac{1}{v}=1-\frac{1}{1.5}$

$\frac{1}{v}=\frac{3-2}{3}=\frac{1}{3}$

$v=3cm$

Magnification, $m=\frac{v}{u}=\frac{3}{-1.5}=-2$

Hence, the correct answer is OPTION C.