[填空题]
Red light from three separate sources passes throo5 d9xr,dbk2 ;yfsi, vugh a diffracpp1qgv-b1l 8 rtion grating with pbq-g 1vl p8r1$ 3.00\times10^{5 }\;lines/m.$ The wavelengths of the three lines are $ 6.56\times10^{-7 }\;m$ (hydrogen), $ 6.50\times10^{ -7}\;m$ (neon), and $6.97 \times10^{ -7}\;m$ (argon). Calculate the angles for the first-order diffraction lines of each of these sources. $\theta_{h}$ $^{\circ}\,$ $\theta_{n}$ $^{\circ}\,$ $\theta_{a}$ $^{\circ}\,$
