[填空题]
A diffraction grating 4 s+m8rdgpp8k has 1byf6njj, yw x69xn a6*fyf u7$ 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$. $^{\circ}\,$
