Question

A hemispherical glass body of radius $10\, cm$ and refractive index $1.5$ is silvered on its curved surface. A small air bubble is $6 \,cm$ below the flat surface inside it along the axis. The position of the image of the air bubble made by the mirror is seen :

• A. 14 cm below flat surface
• B. 30 cm below flat surface
• C. 20 cm below flat surface
• D. 16 cm below flat surface

Answer 1

Answer: (C)

$\frac{1}{V}+\frac{1}{-4}=\frac{1}{-5}$
$\frac{1}{V}=\frac{1}{4}-\frac{1}{5}=\frac{5-4}{20}$
$V=20\, cm$

$I _{1}$ acts as object for plane surface
$d'=\frac{ d }{ n _{ rel }}=\frac{30}{1.5}$
$d '=\frac{300}{15}=20\, cm$
$20\, cm$ below plane surface