Question

An object is placed at 20 cm from a convex mirror of focal length 20 cm, The distance of the image from the pole of the mirror is :

• A. 15 cm
• B. 10 cm
• C. 40 cm
• D. Infinity

Answer 1

The correct option is B 10 cm

Given, $f=20cm,u=-20cm,v=?$

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

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

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

$\frac{1}{v}=\frac{2}{20}$

$v=10cm$

So, the distance of the image from the pole of the mirror is $10cm.$