Question

An air bubble in a glass sphere having 4 cm diameter appears 1 cm from surface nearest to eye when looked along diameter. If ${\mu }_{ga}=1.5$, the distance of bubble from refracting surface is

• A. 1.2 cm
• B. 3.2 cm
• C. 2.8 cm
• D. 1.6 cm

Answer 1

The correct option is A 1.2 cm

Use this formula,
$\frac{{\mu }_2}{v}-\frac{{\mu }_1}{u}=\frac{{\mu }_2-{\mu }_1}{R}$
where u = ?, v = -1 cm, ${\mu }_1=1.5,{\mu }_2=1,R=-2cm$
$\frac{1}{-1}-\frac{1.5}{u}=\frac{1-1.5}{(-2)}\Rightarrow u=-\frac{6}{5}=-1.2cm$