Log1989 problem number 21.20

The beam of light normally falls on the diffraction grating. The diffraction angle for the line, whose wavelength is 589 nm, in the first-order spectrum is 17 degrees 18 minutes. The angle of diffraction of some line in the second-order spectrum is 24 degrees 12 minutes. Find the wavelength of this line and the number of strokes per 1 mm of the lattice.