Answer
wavelength will be greater
Work Step by Step
This is a diffraction grating, so we can look at equation (36-30) to see how the change in wavelength, $\Delta \lambda$, is related to the order, m.
$$\frac{\Delta \theta}{\Delta \lambda}=\frac{m}{d\cos \theta}$$
We can see that the order and the change in wavelength are incersly related, so the change in wavelength is greater in the first order, than in the third order.
