[填空题]
A diffraction grating f z7gejowo1a(;;c8 s5x zwj2z+ium kw xcuz:.o4xj u;l0)2va has $ 6.0\times10^{ 5}\;lines/m$. Find the angular spread in the second-order spectrum between red light of wavelength $ 7.0\times10^{-7 }\;m$ and blue light of wavelength $ 4.5\times10^{-7 }\;m$. $^{\circ}\,$
