Question

In figure find the total magnification after two successive reflections first on $M_1$ and then on $M_2$.

• A. + 1
• B. - 2
• C. + 2
• D. - 1

Answer 1

The correct option is C + 2

For $M_1$,

$\frac{1}{v}+\frac{1}{u}=\frac{1}{f}$
$\frac{1}{v}-\frac{1}{30}=-\frac{1}{20}$
$\Rightarrow v=-60cm$


For $M_2$,
$\frac{1}{v^{\prime }}-\frac{1}{20}=-\frac{1}{10}$
$\Rightarrow v^{\prime }=-60cm$

Net magnification
$M=-\frac{v^{\prime }}{u}=\frac{-60}{-30}=2$