At the interface between two materials having refractive indices $n_1$ and $n_2$,the critical angle for reflection of an electromagnetic wave is $\theta_{1C}$. The $n_2$ material is replaced by another material having refractive index $n_3$,such that the critical angle at the interface between $n_1$ and $n_3$ materials is $\theta_{2C}$. If $n_3 > n_2 > n_1$,$\frac{n_2}{n_3} = \frac{2}{5}$,and $\sin \theta_{2C} - \sin \theta_{1C} = \frac{1}{2}$,then $\theta_{1C}$ is:

• A
  $\sin^{-1}(\frac{1}{3})$
• B
  $\sin^{-1}(\frac{2}{3})$
• C
  $\sin^{-1}(\frac{5}{6})$
• D
  $\sin^{-1}(\frac{1}{6})$