Answer
If $\theta_1$ is greater than the critical angle, then the light does not emerge into the air. Instead, the light is reflected back into the water.
Work Step by Step
$\frac{c_1}{c_2} = \frac{sin~\theta_1}{sin~\theta_2}$
$sin~\theta_2 = \frac{c_2}{c_1}~sin~\theta_1$
If $\theta_2 = 90^{\circ}$, then $sin~\theta_2 = 1$
$\frac{c_2}{c_1}~sin~\theta_1 = 1$, when $\theta_1$ is the critical angle.
If $\theta_1$ is greater than the critical angle, then $\frac{c_2}{c_1}~sin~\theta_1 \gt 1$
This would mean that $sin~\theta_2 \gt 1$, which is not possible.
If $\theta_1$ is greater than the critical angle, then the light does not emerge into the air. Instead, the light is reflected back into the water.
