With light falling normally on a transparent diffraction grating 10 mm wide, it was found that the components of the yellow line of sodium (589.0 and 589.6 nm) are resolved beginning with the fifth order of the spectrum. Evaluate:
(a) the ** of this grating;
(b) what must be the width of the grating with the same ** for a doublet λ = 460.0 nm whose components differ by 0.13 nm to be resolved in the third order of the spectrum.
