Answer
A
Work Step by Step
From the figure, we can see that grating A has smaller half-widths.
This is a diffraction grating, so we can look at equation (36-28) to see how the lengths of the half-widths, $\Delta \theta_{hw}$, are related to the number of rulings, N.
$$\Delta \theta_{hw}=\frac{\lambda}{Nd\cos \theta} $$
We can see that as the number of rulings, N, increases, the half-widths, $\Delta \theta_{hw}$, decrease. Therefore, diffraction grating A has the greater number of rulings.
