Answer
a. 1.40.
b. $35.5^{\circ}$.
Work Step by Step
The sunlight strikes the glass at Brewster’s angle (the polarizing angle) because we know the reflected light is completely polarized.
Equation 33.8 tells us $tan \theta_p=\frac{n_b}{n_a}$.
$$tan 54.5^{\circ}=\frac{n_{glass}}{1.00}$$
$$n_{glass}=1.40$$
b. Use Snell’s Law, where the angles are measured from the normal to the interface.
$$n_a sin\theta_a= n_b sin\theta_b$$
$$\theta_b=sin^{-1}(\frac{n_a}{n_b}sin\theta_1) $$
$$=sin^{-1}(\frac{1.00}{1.40}sin54.5^{\circ}) =35.5^{\circ}$$
