Answer
$4.3^{\circ}$
Work Step by Step
Use equation 24–4 to find the angle for the second-order maximum.
$$d sin \theta = m \lambda $$
$$\theta =sin^{-1}(\frac{m \lambda}{d})$$
$$ =sin^{-1}(\frac{2 (510\times10^{-9}m)}{1.35\times10^{-5}m})$$
$$=4.3^{\circ}$$
