Question

Taking the first reflection of M1. If the final image coincides with s, then find n.

Answer 1

The correct answer is 150

Consider refraction on M1

$\frac{1}{V}+\frac{1}{-10}=\frac{1}{-12}$

$\Rightarrow V=60$

Now, Consider refraction from L

$\frac{1}{V}-\frac{1}{-80}=\frac{1}{-10}\Rightarrow V=\frac{80}{7}$

It is at the focus of M2,

So, $\frac{80}{7}+10=\frac{n}{7}$

$n=150$