Answer
The light emerges back into air at the right at an angle of $~~50^{\circ}$
Work Step by Step
We can use Snell's law to find the refraction angle $\theta_7$ at which the light emerges back into the air:
$n_{air}~sin~\theta_1 = n_1~sin~\theta_2 = n_3~sin~\theta_3 = ...= n_{air}~sin~\theta_7$
$n_{air}~sin~\theta_1 = n_{air}~sin~\theta_7$
$sin~\theta_1 =sin~\theta_7$
$\theta_1 = \theta_7$
$\theta_7 = 50^{\circ}$
The light emerges back into air at the right at an angle of $~~50^{\circ}$
