0^{\circ}$. We can use Snell's Law to find the index of refraction of the liquid:
$n_1 \sin{\theta_1} = n_2 \sin{\theta_2}$
where $n_1$ is the index of refraction of glass, $\theta_1$ is the angle of incidence, $n_2$ is the index of refraction of the liquid, and
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