b
\((b)\) From graph, slope \( = \tan \,\left({\frac{{2\pi }}{{10}}} \right) = \frac{{\sin r}}{{\sin i}}\)

Also \(_1{\mu _2} = \frac{{{\mu _2}}}{{{\mu _1}}} = \frac{{\sin i}}{{\sin r}}= \frac{1}{{\tan \,\left({\frac{{2\pi }}{{10}}} \right)}} = \frac{4}{3}\)

\(⇒\) \({\mu _2} > {\mu _1}\)

It means that medium \(2\) is denser medium. So total internal reflection cannot occur.