Answer
$\theta_A = 54.3^{\circ}$
Work Step by Step
We can use Equation (33-45) to find the critical angle $\theta_c$:
$\theta_c = sin^{-1}~\frac{n_3}{n_2}$
$\theta_c = sin^{-1}~\frac{1.30}{1.80}$
$\theta_c = 46.24^{\circ}$
We can use Snell's law to find $\theta_A$:
$n_1~sin~\theta_A = n_2~sin~\theta_c$
$sin~\theta_A = \frac{n_2~sin~\theta_c}{n_1}$
$\theta_A = sin^{-1}~(\frac{n_2~sin~\theta_c}{n_1})$
$\theta_A = sin^{-1}~(\frac{1.80~sin~46.24^{\circ}}{1.60})$
$\theta_A = sin^{-1}~(0.8125)$
$\theta_A = 54.3^{\circ}$
