With light falling normally on a transparent diffraction grating l0 mm wide, it was found that the

Question:

With light falling normally on a transparent diffraction grating l0 mm wide, it was found that the components of the yellow line of sodium (589.0 and 589.6 rim) are resolved beginning with the fifth order of the spectrum. Evaluate:
(a) The period of this grating;
(b) What must be the width of the grating with the same period for a doublet λ = 460.0 nm whose components differ by 0.13 nm to be resolved in the third order of the spectrum.