Answer
$\theta_3 = 39^{\circ}$
Work Step by Step
In part (a), we found that $n_1 = 1.6$
According to Snell's law:
$n_1~sin~\theta_1 = n_2~sin~\theta_2 = n_3~sin~\theta_3$
We can find $\theta_3$:
$n_1~sin~\theta_1 = n_3~sin~\theta_3$
$sin~\theta_3 = \frac{n_1~sin~\theta_1}{n_3}$
$\theta_3 = sin^{-1}~(\frac{n_1~sin~\theta_1}{n_3})$
$\theta_3 = sin^{-1}~(\frac{1.6~sin~70^{\circ}}{2.4})$
$\theta_3 = sin^{-1}~(0.6265)$
$\theta_3 = 39^{\circ}$
