Answer
1.77.
Work Step by Step
Total internal reflection occurs when the angle of incidence is greater than or equal to the critical angle.
At the critical angle, Snell’s law gives $n_{glass}sin\theta_{crit}= n_{water}sin90^{\circ}$.
$$ n_{glass}sin48.7^{\circ}= 1.333 (1)$$
$$ n_{glass}=\frac{1.333}{ sin48.7^{\circ}} = 1.77$$
