A grating has 500 lines/mm — JEE Physics

$$d = \frac{1}{500 \times 10^3} = 2 \times 10^{-6} m$$

$$d\sin\theta = m\lambda \Rightarrow \sin\theta = \frac{2 \times 600\times10^{-9}}{2\times10^{-6}} = \frac{1.2\times10^{-6}}{2\times10^{-6}} = 0.6$$

$$\theta = \sin^{-1}(0.6) \approx 36.87°$$