question_answer

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

A) 1.2 cm

B) 3.2 cm

C) 2.8 cm

D) 1.6 cm

Correct Answer: A

Solution :

[a]

By using \[\frac{{{\mu }_{2}}}{v}-\frac{{{\mu }_{1}}}{u}=\frac{{{\mu }_{2}}-{{\mu }_{1}}}{R}\]

where \[u=?,\,\,v=-1\,\,cm,\,\,{{\mu }_{1}}=1.5,\,\,{{\mu }_{2}}=1,\,\,R=-2\,cm\]

\[\frac{1}{-1}-\frac{1.5}{u}=\frac{1-1.5}{(-2)}\]

\[\Rightarrow \]   \[u=-\frac{6}{5}\,=-1.2\,cm\]