Question

An object is placed in front of a convex lens, find the linear magnification produced by the lens.

• A. 4
• B. 3
• C. 2
• D. 1

Answer 1

The correct option is A 4

$\frac{1}{v}-\frac{1}{u}=\frac{1}{f}$
$\frac{1}{v}+\frac{1}{30}=\frac{1}{40}$
$\frac{1}{v}=\frac{1}{40}-\frac{1}{30}=\frac{3}{120}-\frac{4}{120}=\frac{-1}{120}$
$v=-120$
$m=\frac{v}{u}=\frac{-120}{-30}=+4$