• # question_answer The refractive index of water is 4/3 and that of glass is 5/3. Then the critical angle for a ray of light entering water from glass will be- A) $si{{n}^{-}}^{1}\left( 4/5 \right)$                   B) ${{\sin }^{-}}^{1}\,\,\left( 5/4 \right)$C) $si{{n}^{-}}^{1}\left( 20/9 \right)~$   D) $si{{n}^{-1}}\,\,\left( 9/20 \right)$

${{\mu }_{w}}=\frac{4}{3}\,\,{{\mu }_{glass}}\,\,=\,\,\frac{5}{3}$ glass is denser medium wrt water. ${{\theta }_{c}}\,\,=\,\,{{\sin }^{-1}}\,\left( \frac{{{\mu }_{r}}}{{{\mu }_{D}}} \right)$ ${{\theta }_{c}}\,\,=\,\,{{\sin }^{-1}}\,\left( \frac{\frac{4}{3}}{\frac{5}{3}} \right)$ ${{\theta }_{c}}\,\,=\,\,{{\sin }^{-1}}\,\left( \frac{4}{5} \right)$