Answer
$\alpha = 0.46rad$
Work Step by Step
Because we know the angle from part 13a, we can use the given values in equation (36-6) to solve for the angle, $\alpha$.
$\alpha = \frac{\pi a}{\lambda}\sin \theta$
$\alpha = \frac{\pi 0.025mm}{538*10^{-6}mm}\sin 0.18^{\circ}$
$\alpha = 0.46rad$
