Question

An object is placed at a distance of 40 cm from a concave lens of focal length 10 cm. Find the image distance.

• A. 10 cm
• B. -10 cm
• C. 8 cm
• D. -8 cm

Answer 1

The correct option is D -8 cm


f = -10 cm
Applying lens formula,
$\frac{1}{v}-\frac{1}{u}=\frac{1}{f}$
$\frac{1}{v}=\frac{1}{f}+\frac{1}{u}=\frac{-1}{10}-\frac{1}{40}=\frac{-1}{8}\Rightarrow v=-8cm.$