Question

A thin plano-concave lens is placed on paper on which a flower is drawn. How far above(in $\text{cm}$) its actual position does the flower appear to an observer looking down from top?

Answer 1

Considering refraction from a curved surface at the air concave surface interface -Refraction from single curved surface
$\frac{{\mu }_2}{v}-\frac{{\mu }_1}{u}=\frac{{\mu }_2-{\mu }_1}{R}$

$\frac{1}{v}-\frac{\frac{3}{2}}{-20}=\frac{1-\frac{3}{2}}{20}$

$\Rightarrow v=-10\text{cm}$
So, the image appears to be 10 cm above the actual position.