Question

An object is placed at a distance of $20cm$ from a convex mirror of focal length $30cm$. Find its magnification.

• A. $1.66$
• B. $1.5$
• C. $0.6$
• D. None

Answer 1

The correct option is C $0.6$

We know, $\frac{1}{v}+\frac{1}{u}=\frac{1}{f}$

$\frac{1}{v}+\frac{1}{-20cm}=\frac{1}{30cm}$

$\frac{1}{v}=\frac{1}{30}+\frac{1}{20}$

$\frac{2+3}{60}=\frac{1}{v}$

$v=12cm$

Therefore, magnification, $m=\frac{-v}{u}$

$=\frac{-12}{-20}=0.6cm$