Question

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

• A. 13.3 cm
• B. 20 cm
• C. 25 cm
• D. 10 cm

Answer 1

Answer: (D)

10 cm

Answer 2

$u =-20\, cm,\, f =20\, cm$
From mirror formula,
$\frac{1}{ f }=\frac{1}{ v }+\frac{1}{ u }$
$\frac{1}{20}=\frac{1}{ v }+\frac{1}{-20}$
$\frac{1}{ v }=\frac{1}{20}+\frac{1}{20}$
$\frac{1}{ v }=\frac{2}{20}$
$\Rightarrow v =10\, cm$