Physics

Solution:

$μ_{2}=1.5$ and $f_{air}=10cm$

$f$ of 2 plano convex lenses $=f$ of a biconvex lens $=2f_{air}=20cm$

So, $f_{liq}f_{air} $ = $μ_{g}−1μ_{l}μ_{g} −1 $ = $1.5−11.125−1 $

And, $f_{liq}=80cm$

$f_{eq}=f_{1}+f_{2}f_{1}f_{2} =10080×80 =40cm$

$v1 −u1 =f1 $

$v1 −−151 =301 $

$v1 =301 −151 $

$v1 =30−1 $

$v=−30$