Number of lines per millimeter on grating good. Grating constant d (m) 0.00167 mm = 16,700 A TABLE 1 HYDROGEN VAPOR TUBE Color of Divided circle Wavelength in Standard %% error Spectrum line reading 20 sin 0 Angstroms, A" Wavelength Right Left Angstroms, A Violet(v) 42 -40 82 41 0.6561 10956.87 4100 Text Blueviolet(bv) Text Text Text Text Text Text 4400 Text Blue green (bg) Text Text Text Text Text Text 4925 Text Red(r) Text Text Text Text Text Text 7000 Text